Publications by category
Books
Hodgson, D.J. Tregenza, T. (2008). Comparative evidence for strong phylogenetic inertia in precloacal signalling glands in a species-rich lizard clade.
Journal articles
Cornell S, Tregenza T (In Press). A new theory for the evolution of polyandry. Proceedings of the Royal Society B: Biological Sciences
Price N, Green S, Troscianko J, Tregenza T, Stevens M (In Press). Background matching and disruptive coloration as habitat-specific strategies for camouflage. Scientific Reports
Carter EE, Tregenza T, Stevens M (In Press). Ship noise inhibits colour change, camouflage, and anti-predator behaviour in shore crabs. Current Biology
Rodríguez-Muñoz R, Hopwood P, Boonekamp JJ, Edwards SA, Price TW, Rees J, Tregenza T (2023). Local adaptation does not constrain the expression of behaviour in translocated wild crickets.
Animal Behaviour,
200, 15-23.
Abstract:
Local adaptation does not constrain the expression of behaviour in translocated wild crickets
Behaviour has the potential to retard evolutionary adaptation by equipping animals with the capacity to radically change their interactions with the environment without evolving. Despite this potential for plasticity, laboratory studies frequently identify among-population differences in responses to identical stimuli, suggesting that genetic adaption often reduces behavioural flexibility. However, laboratory environments are typically far removed from nature, so their relevance to the variation we might expect to see in the wild (either among environments or as a result of changes in climate) is unclear. This is a particularly acute issue in relation to behaviour because behaving in an optimal fashion requires animals to receive and process complex sensory information which may be disrupted by laboratory conditions. We translocated newly adult male field crickets, Gryllus campestris, from five high-altitude and five low-altitude populations into a single low-altitude meadow from which we had removed all naturally present males. By tagging every individual and employing a network of 140 video cameras we were able to record comprehensive behavioural information from early adulthood until death. This allowed us to directly compare the behaviour of individuals from populations known to be genetically divergent and adapted to either high or low altitudes. We found very limited evidence for an effect on behaviour of the altitudinal environment in which crickets had evolved and developed, despite the large scale of our study (>20 000 h of observations of 128 males). Our findings suggests that when provided with all the environmental cues present in their natural environment, local adaptation does not lead to substantial constraints on behaviour. This supports the hypothesis that the potential flexibility of behaviour may tend to reduce selection for local adaptation.
Abstract.
Wilde JA, Rodríguez-Muñoz R, Darden SK, Tregenza T, Fawcett TW (2023). Signalling males increase or decrease their calling effort according to the proximity of rivals in a wild cricket.
Animal Behaviour,
203, 53-61.
Abstract:
Signalling males increase or decrease their calling effort according to the proximity of rivals in a wild cricket
Males that employ dynamic courtship displays to attract females may tactically adjust their courtship in response to their social environment. However, we know little about how sexual signals are adjusted in complex natural settings, where individuals are competing for attention against a backdrop of signals from nearby and distant rivals. We investigated this using data from the WildCrickets project, a wild population of field crickets, Gryllus campestris, continuously monitored via CCTV cameras. We used over a million scan samples from 129 males across 51 days to explore how the singing and proximity of other males influenced male singing behaviour. We first quantified the spatial network of the males to understand how the extent of singing overlap is affected by the distance between them, and found a moderate overlap across the whole population, regardless of distance. We then used a finer-grained analysis controlling for the effect of environmental variables. At distances greater than 1 m, we found a stimulatory effect of singing by other males on a focal male's singing behaviour, leading to males singing in the same time intervals. The overlap in singing became weaker as the distance between males increased. Conversely, we found that males were less likely to call when another male was singing very close by (within 1 m), suggesting an inhibitory effect. These findings reveal how, in a dynamic social network in a wild population, males perform fine-scale adjustments to their signalling behaviour in response to signalling by other males both nearby and far away.
Abstract.
Aagaard A, Liu S, Tregenza T, Braad Lund M, Schramm A, Verhoeven KJF, Bechsgaard J, Bilde T (2022). Adapting to climate with limited genetic diversity: Nucleotide, DNA methylation and microbiome variation among populations of the social spider Stegodyphus dumicola.
Mol Ecol,
31(22), 5765-5783.
Abstract:
Adapting to climate with limited genetic diversity: Nucleotide, DNA methylation and microbiome variation among populations of the social spider Stegodyphus dumicola.
Understanding the role of genetic and nongenetic variants in modulating phenotypes is central to our knowledge of adaptive responses to local conditions and environmental change, particularly in species with such low population genetic diversity that it is likely to limit their evolutionary potential. A first step towards uncovering the molecular mechanisms underlying population-specific responses to the environment is to carry out environmental association studies. We associated climatic variation with genetic, epigenetic and microbiome variation in populations of a social spider with extremely low standing genetic diversity. We identified genetic variants that are associated strongly with environmental variation, particularly with average temperature, a pattern consistent with local adaptation. Variation in DNA methylation in many genes was strongly correlated with a wide set of climate parameters, thereby revealing a different pattern of associations than that of genetic variants, which show strong correlations to a more restricted range of climate parameters. DNA methylation levels were largely independent of cis-genetic variation and of overall genetic population structure, suggesting that DNA methylation can work as an independent mechanism. Microbiome composition also correlated with environmental variation, but most strong associations were with precipitation-related climatic factors. Our results suggest a role for both genetic and nongenetic mechanisms in shaping phenotypic responses to local environments.
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Author URL.
Tregenza T, Niemelä PT, Rodríguez-Muñoz R, Hopwood PE (2022). Environment and mate attractiveness in a wild insect.
Behavioral Ecology,
33(5), 999-1006.
Abstract:
Environment and mate attractiveness in a wild insect
AbstractThe role of female choice in sexual selection is well established, including the recognition that females choose their mates based on multiple cues. These cues may include intrinsic aspects of a male’s phenotype as well as aspects of the environment associated with the male. The role of the spatial location of a potential mate has been well studied in territorial vertebrates. However, despite their role as laboratory models for studies of sexual selection, the potential for insects to choose their mates on the basis of location has scarcely been studied. We studied a natural population of individually tagged crickets (Gryllus campestris) in a meadow in Northern Spain. Adults typically move between burrows every few days, allowing us to examine how pairing success of males can be predicted by the burrow they occupy, independent of their own characteristics. We observed the entirety of ten independent breeding seasons to provide replication and to determine whether the relative importance of these factors is stable across years. We find that both male ID and the ID his burrow affect the likelihood that he is paired with a female, but the burrow has a consistently greater influence. Furthermore, the two factors interact: the relative attractiveness of an individual male depends on which burrow he occupies. Our finding demonstrates a close interaction between naturally and sexually selected traits. It also demonstrates that mate choice studies may benefit from considering not only obvious secondary sexual traits, but also more cryptic traits such as microhabitat choice.
Abstract.
Boonekamp J, Rodríguez-Muñoz R, Hopwood P, Zuidersma E, Mulder E, Wilson A, Verhulst S, Tregenza T (2022). Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets.
Mol Ecol,
31(23), 6128-6140.
Abstract:
Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets.
Many organisms are capable of growing faster than they do. Restrained growth rate has functionally been explained by negative effects on lifespan of accelerated growth. However, the underlying mechanisms remain elusive. Telomere attrition has been proposed as a causal agent and has been mostly studied in endothermic vertebrates. We established that telomeres exist as chromosomal-ends in a model insect, the field cricket Gryllus campestris, using terminal restriction fragment and Bal 31 methods. Telomeres comprised TTAGGn repeats of 38 kb on average, more than four times longer than the telomeres of human infants. Bal 31 assays confirmed that telomeric repeats were located at the chromosome-ends. We tested whether rapid growth between day 1, day 65, day 85, and day 125 is achieved at the expense of telomere length by comparing nymphs reared at 23°C with their siblings reared at 28°C, which grew three times faster in the initial 65 days. Surprisingly, neither temperature treatment nor age affected average telomere length. Concomitantly, the broad sense heritability of telomere length was remarkably high at ~100%. Despite high heritability, the evolvability (a mean-standardized measure of genetic variance) was low relative to that of body mass. We discuss our findings in the context of telomere evolution. Some important features of vertebrate telomere biology are evident in an insect species dating back to the Triassic. The apparent lack of an effect of growth rate on telomere length is puzzling, suggesting strong telomere length maintenance during the growth phase. Whether such maintenance of telomere length is adaptive remains elusive and requires further study investigating the links with fitness in the wild.
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Author URL.
Tregenza T, Rodríguez-Muñoz R, Boonekamp JJ, Hopwood PE, Sørensen JG, Bechsgaard J, Settepani V, Hegde V, Waldie C, May E, et al (2021). Evidence for genetic isolation and local adaptation in the field cricket Gryllus campestris.
J Evol Biol,
34(10), 1624-1636.
Abstract:
Evidence for genetic isolation and local adaptation in the field cricket Gryllus campestris.
Understanding how species can thrive in a range of environments is a central challenge for evolutionary ecology. There is strong evidence for local adaptation along large-scale ecological clines in insects. However, potential adaptation among neighbouring populations differing in their environment has been studied much less. We used RAD sequencing to quantify genetic divergence and clustering of ten populations of the field cricket Gryllus campestris in the Cantabrian Mountains of northern Spain, and an outgroup on the inland plain. Our populations were chosen to represent replicate high and low altitude habitats. We identified genetic clusters that include both high and low altitude populations indicating that the two habitat types do not hold ancestrally distinct lineages. Using common-garden rearing experiments to remove environmental effects, we found evidence for differences between high and low altitude populations in physiological and life-history traits. As predicted by the local adaptation hypothesis, crickets with parents from cooler (high altitude) populations recovered from periods of extreme cooling more rapidly than those with parents from warmer (low altitude) populations. Growth rates also differed between offspring from high and low altitude populations. However, contrary to our prediction that crickets from high altitudes would grow faster, the most striking difference was that at high temperatures, growth was fastest in individuals from low altitudes. Our findings reveal that populations a few tens of kilometres apart have independently evolved adaptations to their environment. This suggests that local adaptation in a range of traits may be commonplace even in mobile invertebrates at scales of a small fraction of species' distributions.
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Author URL.
Pincheira-Donoso D, Harvey LP, Grattarola F, Jara M, Cotter SC, Tregenza T, Hodgson DJ (2021). The multiple origins of sexual size dimorphism in global amphibians.
Global Ecology and Biogeography,
30(2), 443-458.
Abstract:
The multiple origins of sexual size dimorphism in global amphibians
Aim: Body size explains most of the variation in fitness within animal populations and is therefore under constant selection from ecological and reproductive pressures, which often promote its evolution in sex-specific directions, leading to sexual size dimorphism (SSD). Several hypotheses have been proposed to explain the vast diversity of SSD across species. These hypotheses emphasize: (a) the mate competition benefits to larger male size (sexual selection); (b) the benefits of larger female size for fecundity (fecundity selection); (c) the simultaneous benefits of niche divergence for males and females to reduce intersexual competition for ecological resources (natural selection); and (d) the underlying impact of geographical variation in climatic pressures expected to shape large-scale patterns of SSD in synergy with the above selection pressures (e.g. intensification of fecundity selection as breeding seasons shorten). Based on a new, global-scale amphibian dataset, we address the shortage of large-scale, integrative tests of these four hypotheses. Location: Global. Time period: Extant. Major taxa studied: Class Amphibia. Methods: Using a > 3,500 species dataset spanning body size, ecological, life-history, geographical and climatic data, we performed phylogenetic linear models to address the sexual, fecundity, ecological and climatic hypotheses of SSD. Results: Evolution of SSD is discordant between anurans and salamanders. Anuran SSD is shaped by climate (male-biased SSD increases with temperature seasonality) and by nesting site. In salamanders, SSD converges across species that occupy the same types of microhabitats (“ecodimorphs”), whereas reproductive or climatic pressures have no effects on their SSD. These contrasts are associated with latitudinal gradients of SSD in anurans, but not in salamanders. Main conclusions: Amphibian SSD is driven by ecological and climatic pressures, whereas no roles for sexual or fecundity selection were detected. We show that macroevolutionary processes determined by different forms of selection lead to latitudinal patterns of trait diversity, and the lack of them.
Abstract.
Zhou J, Zhang J, Tregenza T, Pan Y, Wang Q, Shi H, Liu X (2020). Larval Host Preference and Suitability for the Sawfly Mesoneura rufonota among Five Cinnamomun Tree Species.
Insects,
11(2).
Abstract:
Larval Host Preference and Suitability for the Sawfly Mesoneura rufonota among Five Cinnamomun Tree Species.
The camphor sawfly, Mesoneura rufonota Rohwer, is an economically important leaf-chewing pest of the genus Cinnamomum Trew. However, little is known about the range of species that it can infest within this genus or whether larvae show preferences for particular species. We conducted preference and performance experiments under laboratory conditions to assess larval host preference and suitability as a host plant of five congeneric trees species: C. camphora (Linn) Presl, C. bodinieri Levl. C. burmanni (Nees et T. Nees) Blume, C. pauciflorum Nees, and C. micranthum (Hay.) Hay. In no-choice, two-choice and multiple-choice feeding trials, significantly higher feeding rates were found on C. camphora, followed by C. bodinieri, compared to those on the other three tree species. In two-choice behavior trials, larvae moved to occupy leaves of C. camphora faster and more frequently, followed by C. bodinieri, than when offered the other three tree species. In no-choice fitness trials, the survival of larval and pupal stage was the highest, the developmental duration of larval and pupal stage was the shortest, the pupal body weight was the heaviest and adults lived the longest on C. camphora followed by C. bodinieri, while M. rufonota did not complete development on C. burmanni, C. pauciflorum or C. micranthum. Our results demonstrate that larvae consistently prefer and perform better on C. camphora leaves, that they can utilize C. bodinieri, but it is less preferred, and that C. burmanni, C. pauciflorum, and C. micranthum appear to be unsuitable as a host for M. rufonota.
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Author URL.
Makai G, Rodríguez-Muñoz R, Boonekamp JJ, Hopwood P, Tregenza T (2020). Males and females differ in how their behaviour changes with age in wild crickets.
Animal Behaviour,
164, 1-8.
Abstract:
Males and females differ in how their behaviour changes with age in wild crickets
Because females produce and lay eggs or nurture embryos, they are constrained in the timing of their investment in reproduction. Males may have more opportunity to concentrate reproductive investment earlier in life, mating with as many females as possible soon after becoming adult. This fundamental difference leads to the prediction that because males can bias allocation towards increased reproductive investment early in life, they will use up resources earlier in their lives and hence senesce faster than females. A first step towards testing this prediction is to determine whether there are between-sex differences in age-related changes in behaviour. To do this we recorded the behaviour of crickets, Gryllus campestris, in a natural population living in and around their burrows in a meadow in northern Spain. Following individuals of both sexes through their adult lives, we recorded a range of nonreproductive behaviours, including how often they moved in and out of their burrows, how long they spent at the entrance, how long they spent outside, how quickly they left a burrow after fleeing inside to escape predation and whether they fed. We found evidence for substantial age-related changes in two of the movement traits in males, but not in females. Males moved less often and spent less time outside their burrows as they aged, whereas females showed no age-related changes in either trait. Feeding was not affected by age in males, but females fed more often as they got older. Our findings are consistent with the prediction that males senesce faster than females; experiments in nature will be needed to determine whether this pattern arises from life history trade-offs between reproduction and other traits.
Abstract.
Boonekamp J, Rodríguez-Muñoz R, Hopwood P, Zuidersma E, Mulder E, Wilson A, Verhulst S, Tregenza T (2020). Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets.
Abstract:
Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets
AbstractMany organisms are capable of growing faster than they do. Restrained growth rate has functionally been explained by negative effects on lifespan of accelerated growth. However, the underlying mechanisms remain elusive. Telomere attrition has been proposed as a causal agent and has been studied in endothermic vertebrates. We established that telomeres exist as chromosomal-ends in a model insect, the field cricket, using terminal restriction fragment andBal 31methods. Telomeres comprised TTAGGn repeats of 38kb on average, more than four times longer than the telomeres of human infants.Bal 31assays confirmed that telomeric repeats were located at the chromosome-ends. We tested whether rapid growth is achieved at the expense of telomere length by comparing crickets reared at 23°C with their siblings reared at 28°C, which grew three times faster. Surprisingly, neither temperature treatment nor age affected average telomere length. Concomitantly, the broad sense heritability of telomere length was remarkably high at ~100%. Despite high heritability, the evolvability (a mean standardized measure of genetic variance) was low relative to that of body mass. We discuss the different interpretations of these scaling methods in the context of telomere evolution. It is clear that some important features of vertebrate telomere biology are evident in an insect species dating back to the Triassic, but also that there are some striking differences. The apparent lack of an effect of growth rate and the total number of cell divisions on telomere length is puzzling, suggesting that telomere length could be actively maintained during the growth phase. Whether such maintenance of telomere length is adaptive remains elusive and requires further study investigating the links with fitness in the wild.
Abstract.
Rodríguez-Muñoz R, Boonekamp JJ, Liu XP, Skicko I, Haugland Pedersen S, Fisher DN, Hopwood P, Tregenza T (2019). Comparing individual and population measures of senescence across 10 years in a wild insect population.
Evolution,
73(2), 293-302.
Abstract:
Comparing individual and population measures of senescence across 10 years in a wild insect population.
Declines in survival and performance with advancing age (senescence) have been widely documented in natural populations, but whether patterns of senescence across traits reflect a common underlying process of biological ageing remains unclear. Senescence is typically characterized via assessments of the rate of change in mortality with age (actuarial senescence) or the rate of change in phenotypic performance with age (phenotypic senescence). Although both phenomena are considered indicative of underlying declines in somatic integrity, whether actuarial and phenotypic senescence rates are actually correlated has yet to be established. Here we present evidence of both actuarial and phenotypic senescence from a decade-long longitudinal field study of wild insects. By tagging every individual and using continuous video monitoring with a network of up to 140 video cameras, we were able to record survival and behavioral data on an entire adult population of field crickets. This reveals that both actuarial and phenotypic senescence vary substantially across 10 annual generations. This variation allows us to identify a strong correlation between actuarial and phenotypic measures of senescence. Our study demonstrates age-related phenotypic declines reflected in population level mortality rates and reveals that observations of senescence in a single year may not be representative of a general pattern.
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Author URL.
Dutta R, Reddy M, Tregenza T (2019). Discovery of an acoustically locating parasitoid with a potential role in divergence of song types among sympatric populations of the bush cricket Mecopoda elongata.
Journal of Orthoptera Research,
28(2), 181-186.
Abstract:
Discovery of an acoustically locating parasitoid with a potential role in divergence of song types among sympatric populations of the bush cricket Mecopoda elongata
The bush cricket Mecopoda elongata provides a striking example of sympatric intraspecific divergence in mating signals. Five completely distinct song types are found in various parapatric and sympatric locations in South India. While there is convincing evidence that population divergence in M. elongata is being maintained as a result of divergence in acoustic signals, cuticular chemical profiles, and genital characters, the causes of the evolution of such divergence in the first place are unknown. We describe the discovery of a tachinid parasitoid with an orthopteroid hearing mechanism affecting M. elongata. This parasitoid may have a role in driving the extraordinary divergence that had occurred among M. elongata song types. Over two years we sampled individuals of three sympatric song types in the wild and retained individuals in captivity to reveal rates of parasitization. We found that all three song types were infected with the parasitoid but that there were significant differences among song types in their probability of being infected. The probability of tachinid parasitization also differed between the two sampling periods. Therefore, it is possible that parasitoid infection plays a role in song type divergence among sympatric bush cricket populations.
Abstract.
Fisher DN, Rodríguez-Muñoz R, Tregenza T (2019). Dynamic networks of fighting and mating in a wild cricket population.
Animal Behaviour,
155, 179-188.
Abstract:
Dynamic networks of fighting and mating in a wild cricket population
Reproductive success is often highly skewed in animal populations. Yet the processes leading to this are not always clear. Similarly, connections in animal social networks are often nonrandomly distributed, with some individuals with many connections and others with few, yet whether there are simple explanations for this pattern has not been determined. Numerous social interactions involve dyads embedded within a wider network. As a result, it may be possible to model which individuals accumulate social interactions through a more general understanding of the social network's structure, and how this structure changes over time. We analysed fighting and mating interactions across the breeding season in a population of wild field crickets under surveillance from a network of video cameras. We fitted stochastic actor-oriented models to determine the dynamic process by which networks of cricket fighting and mating interactions form, and how they co-influence each other. We found crickets tended to fight those in close spatial proximity to them and those possessing a mutual connection in the fighting network, and heavier crickets fought more often. We also found that crickets that mated with many others tended to fight less in the following time period. This demonstrates that a mixture of spatial constraints, characteristics of individuals and characteristics of the immediate social environment are key for determining social interactions. The mating interaction network required very few parameters to understand its growth and thus its structure; only homophily by mating success was required to simulate the skew of mating interactions seen in this population. This demonstrates that relatively simple, but dynamic, processes can give highly skewed distributions of mating success.
Abstract.
Rodríguez-Muñoz R, Hopwood P, Fisher D, Skicko I, Tucker R, Woodcock K, Slate J, Walling C, Tregenza T (2019). Older males attract more females but get fewer matings in a wild field cricket.
Animal Behaviour,
153, 1-14.
Abstract:
Older males attract more females but get fewer matings in a wild field cricket
The age of potential mates has been proposed to be an important target for mate choice by females. Alternative hypotheses predict preferences in either direction. Females might be expected to prefer older males because such males have demonstrated their capacity to survive. Alternatively, they might prefer younger males that have not accumulated deleterious mutations. Preferences in both directions have been observed in laboratory experiments, suggesting that this is an issue that needs to be understood within its ecological context. We measured individual behaviour and reproductive success in a natural population of the field cricket Gryllus campestris over 10 years. We found that in this annual insect, a male's age relative to his peers was poorly correlated with his life span. This suggests that there is limited potential for selection to favour female choice for older males because a strategy of choosing older males would not significantly increase a female's likelihood of mating with a long-lived male. Older males were more successful at pairing up with females at a burrow, but once paired they were less likely to mate with them. By genotyping the next generation of adults we confirmed that observations of both pairing up with a female and matings were associated with successful offspring production. However, there was no relationship between how old a male was at mating and how many adult offspring he had. This lack of evidence for any fitness benefits to females from mate choice in relation to male age was consistent with the observation that the age of males had opposite effects on their success in pairing up with females compared to their success in mating with them.
Abstract.
Rodríguez-Muñoz R, Boonekamp JJ, Fisher D, Hopwood P, Tregenza T (2019). Slower senescence in a wild insect population in years with a more female-biased sex ratio.
Proc Biol Sci,
286(1900).
Abstract:
Slower senescence in a wild insect population in years with a more female-biased sex ratio.
Life-history theories of senescence are based on the existence of a trade-off in resource allocation between body maintenance and reproduction. This putative trade-off means that environmental and demographic factors affecting the costs of reproduction should be associated with changes in patterns of senescence. In many species, competition among males is a major component of male reproductive investment, and hence variation in the sex ratio is expected to affect rates of senescence. We test this prediction using nine years of demographic and behavioural data from a wild population of the annual field cricket Gryllus campestris. Over these generations, the sex ratio at adulthood varied substantially, from years with an equal number of each sex to years with twice as many females as males. Consistent with the predictions of theory, we found that in years with a greater proportion of females, both sexes experienced a slower increase in mortality rate with age. Additionally, phenotypic senescence in males was slower in years when there were more females. Sex ratio did not affect the baseline mortality rate in males, but females suffered higher age-independent mortality rates when males were in short supply.
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Author URL.
Rodríguez-Muñoz R, Boonekamp JJ, Liu XP, Skicko I, Fisher DN, Hopwood P, Tregenza T (2019). Testing the effect of early-life reproductive effort on age-related decline in a wild insect.
Evolution,
73(2), 317-328.
Abstract:
Testing the effect of early-life reproductive effort on age-related decline in a wild insect.
The disposable soma theory of ageing predicts that when organisms invest in reproduction they do so by reducing their investment in body maintenance, inducing a trade-off between reproduction and survival. Experiments on invertebrates in the lab provide support for the theory by demonstrating the predicted responses to manipulation of reproductive effort or lifespan. However, experimental studies in birds and evidence from observational (nonmanipulative) studies in nature do not consistently reveal trade-offs. Most species studied previously in the wild are mammals and birds that reproduce over multiple discrete seasons. This contrasts with temperate invertebrates, which typically have annual generations and reproduce over a single season. We expand the taxonomic range of senescence study systems to include life histories typical of most temperate invertebrates. We monitored reproductive effort, ageing, and survival in a natural field cricket population over ten years to test the prediction that individuals investing more in early-reproduction senesce faster and die younger. We found no evidence of a trade-off between early-life reproductive effort and survival, and only weak evidence for a trade-off with phenotypic senescence. We discuss the possibility that organisms with multiple discrete breeding seasons may have greater opportunities to express trade-offs between reproduction and senescence.
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Author URL.
Ørskov CK, Tregenza T, Overgaard J (2019). Using radiotelemetry to study behavioural thermoregulation in insects under field conditions.
Methods in Ecology and Evolution,
10(10), 1773-1782.
Abstract:
Using radiotelemetry to study behavioural thermoregulation in insects under field conditions
Thermoregulation is a central aspect of animal physiology. Mobile ectotherms have the potential to influence their temperature through their location and orientation. Behavioural thermoregulation has been extensively studied in insects, particularly in the migratory locust Locusta migratoria. However, most field studies are confined to daytime observations typically using invasive thermocouples with obvious potential to disrupt natural behaviour. We demonstrate that miniature radiotransmitters represent an alternative and less invasive method to study insect thermoregulation. We discuss how this method can be used to study the thermal behaviour of free-ranging animals for extended periods. Specifically, we show that there is a close correlation between temperature recordings from implanted thermocouples in locusts L. migratoria and externally mounted radiotransmitters on the same animals. Our experiments match earlier observations of locust thermoregulatory behaviour confirming that the locusts with transmitters exhibit ‘normal’ thermoregulatory responses to feeding and to infections (behavioural fever). Finally, we demonstrate the practicality of a radiotransmitter-based system by recording natural thermoregulatory behaviour of locusts in a semi-field setting. Our field study showed locusts actively chose warm microclimates during the day and cold microclimates at night. We conclude that the use of radiotelemetry in studies of behavioural thermoregulation in wild insects could provide unique continuous recordings of body temperature over several days. Such data will provide researchers with a more complete understanding of how insects use behavioural thermoregulation in nature.
Abstract.
Dutta R, Balakrishnan R, Tregenza T (2018). Divergence in potential contact pheromones and genital morphology among sympatric song types of the bush cricket Mecopoda elongata.
Frontiers in Ecology and Evolution,
6(OCT).
Abstract:
Divergence in potential contact pheromones and genital morphology among sympatric song types of the bush cricket Mecopoda elongata
A well-established route to speciation in animals is via the evolution of divergent male mating signals and female preferences within a species. However, an open question is how common it is for near complete isolation to be achieved through a single signal-receiver system as opposed to multiple aspects of the mate-recognition system diverging simultaneously. The five highly divergent mate-attraction song types of the bush cricket Mecopoda elongata exemplify reproductive isolation in sympatry through long-distance mating signals. Female preference for their own song type has been established as a strong pre-mating reproductive barrier, but the potential existence of additional isolating mechanisms has not been investigated. We quantify divergence in cuticular lipid profiles and external genital structures between song types. These traits show significant variation among species of Orthoptera and are known to be used in mate recognition following contact. We show that divergence among sympatric Mecopoda song types in both cuticular lipid profiles and two external genital structures is sufficiently extensive that either of them can be used to identify individual song type with 90% accuracy. Our findings suggest that multiple isolating mechanisms are likely to evolve simultaneously facilitating a more robust reproductive isolation. Our study indicates a role for sexual selection in the divergence and potential future speciation of these populations and suggests that reproductive isolation may frequently evolve through simultaneous divergence across different aspects of mate recognition systems.
Abstract.
Fisher DN, David M, Rodriguez-Munoz R, Tregenza T (2018). Lifespan and age, but not residual reproductive value or condition, are related to behaviour in wild field crickets.
ETHOLOGY,
124(5), 338-346.
Author URL.
Pincheira-Donoso D, Tregenza T, Butlin RK, Hodgson DJ (2018). Sexes and species as rival units of niche saturation during community assembly.
Global Ecology and Biogeography,
27(5), 593-603.
Abstract:
Sexes and species as rival units of niche saturation during community assembly
Aim: Community assembly is traditionally assumed to result from speciation and colonization mediated by available niche space. This paradigm is expanded by the theory that niche space can also be saturated by intersexual adaptive divergence (ecological sexual dimorphism) when interspecific competition is relaxed. This theory (here termed ‘niche-packing equivalence’) predicts that the evolution of ecological sexual dimorphism constrains the ecological opportunity that would otherwise lead to ecological speciation or colonization, and that saturation of niches by different species constrains divergent selection for divergence between the sexes. Therefore, sexes and species are equivalent, yet antagonistic units of niche occupation. We present the most comprehensive test of the niche-packing equivalence theory at ecological time-scales (assemblage level) to date. Location: South America. Major taxa studied: Liolaemus lizards. Methods: We identified 23 Liolaemus assemblages varying in species richness and sexual size dimorphism (SSD), distributed across a wide environmental range. We used mixed effects models, permutation tests and Markov Chain Monte Carlo (MCMC) regressions to quantify the relationship between SSD and species richness. We then partitioned the body size niche dimension between the sexes and amongst species, and tested for non-overlapping body size distributions. We regressed SSD and species richness of each assemblage against environmental predictors, using multi-model inference and structural equation modelling. Results: Sexual dimorphism declines with increasing species richness, and a strong signal of tension between the two remains following phylogenetic control. This pattern is accompanied by evidence of constraints on body-size partitioning amongst species and between the sexes: the two units of niche saturation tend not to overlap. However, across assemblages, species richness and SSD correlate with different environmental variables, suggesting that their tension is context-specific. Main conclusions: Our evidence supports the prediction that sexual dimorphism and species richness are alternative outcomes of adaptive radiation. However, this antagonism is mediated by a suite of environmental predictors that influence dimorphism and species richness differentially.
Abstract.
Fisher DN, Ilany A, Silk MJ, Tregenza T (2017). Analysing animal social network dynamics: the potential of stochastic actor‐oriented models.
Journal of Animal Ecology,
86(2), 202-212.
Abstract:
Analysing animal social network dynamics: the potential of stochastic actor‐oriented models
Summary
Animals are embedded in dynamically changing networks of relationships with conspecifics. These dynamic networks are fundamental aspects of their environment, creating selection on behaviours and other traits. However, most social network‐based approaches in ecology are constrained to considering networks as static, despite several calls for such analyses to become more dynamic.
There are a number of statistical analyses developed in the social sciences that are increasingly being applied to animal networks, of which stochastic actor‐oriented models (SAOMs) are a principal example. SAOMs are a class of individual‐based models designed to model transitions in networks between discrete time points, as influenced by network structure and covariates. It is not clear, however, how useful such techniques are to ecologists, and whether they are suited to animal social networks.
We review the recent applications of SAOMs to animal networks, outlining findings and assessing the strengths and weaknesses of SAOMs when applied to animal rather than human networks. We go on to highlight the types of ecological and evolutionary processes that SAOMs can be used to study.
SAOMs can include effects and covariates for individuals, dyads and populations, which can be constant or variable. This allows for the examination of a wide range of questions of interest to ecologists. However, high‐resolution data are required, meaning SAOMs will not be useable in all study systems. It remains unclear how robust SAOMs are to missing data and uncertainty around social relationships.
Ultimately, we encourage the careful application of SAOMs in appropriate systems, with dynamic network analyses likely to prove highly informative. Researchers can then extend the basic method to tackle a range of existing questions in ecology and explore novel lines of questioning.
Abstract.
Baxter SW, Hoffman JI, Tregenza T, Wedell N, Hosken DJ (2017). EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly.
Heredity (Edinb),
118(4), 322-329.
Abstract:
EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly.
Understanding selection in the wild remains a major aim of evolutionary ecology and work by Ford and colleagues on the meadow brown butterfly Maniola jurtina did much to ignite this agenda. A great deal of their work was conducted during the 1950s on the Isles of Scilly. They documented island-specific wing-spot patterns that remained consistent over about a decade, but patterns on some islands changed after environmental perturbation. It was suggested that these wing-spot patterns reflected island-specific selection and that there was little migration between islands. However, genetic studies to test the underlying assumption of restricted migration are lacking and it is also unknown whether the originally described wing-spot patterns have persisted over time. We therefore collected female butterflies from five of Ford's original study locations, including three large islands (St Mary's, St Martin's and Tresco) and two small islands (Tean and St Helen's). Wing-spot patterns had not changed appreciably over time on three of the islands (two large and one small), but were significantly different on the other two. Furthermore, analysis of 176 amplified fragment length polymorphisms revealed significant genome-wide differentiation among the five islands. Our findings are consistent with Ford's conclusions that despite the close proximity of these islands, there is restricted gene flow among them.
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Author URL.
Dutta R, Tregenza T, Balakrishnan R (2017). Reproductive isolation in the acoustically divergent groups of tettigoniid, Mecopoda elongata.
PLoS One,
12(11).
Abstract:
Reproductive isolation in the acoustically divergent groups of tettigoniid, Mecopoda elongata.
Sympatric divergent populations of the same species provide an opportunity to study the evolution and maintenance of reproductive isolation. Male mating calls are important in sexual selection in acoustically communicating species, and they also have the potential to maintain isolation among species or incipient species. We studied divergent south Indian populations of the bush cricket Mecopoda elongata which are extremely difficult to distinguish morphologically, but which exhibit striking divergence in male acoustic signals. We performed phonotactic experiments investigating the relative preference of females of the "Chirper" song type for calls of all 5 of the song types found in the region (in varying degrees of sympatry). We found that Chirper females preferred their own song type and were completely unresponsive to three trilling song types. Chirper females were occasionally attracted to the call type "Double Chirper" (the call most similar to their own type), suggesting call preference alone cannot provide a complete isolating mechanism. To investigate the basis of call preference we investigated the response of chirper females to variation in chirp rate. Chirper females responded most frequently to a mean chirp rate characteristic of their own song type rather than a higher chirp rate which would be more characteristic of the Double-Chirper song type. This suggests females drive stabilising selection on male chirp rate, which may contribute to the maintenance of isolation. Finally, a no-choice mating experiment using Chirper females and Chirper and Double Chirper males revealed a significant preference of Chirper females to mate with their own song type, even without a requirement for phonotaxis. Overall, the strong specificity of Chirper females for their 'own' song type provides evidence for behavioural isolation among divergent sympatric Mecopoda song types being maintained by female preference for both male song type and subsequent mating probability driven by other cues.
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Author URL.
Fisher DN, Rodríguez-Muñoz R, Tregenza T (2016). Comparing pre- and post-copulatory mate competition using social network analysis in wild crickets.
Behav Ecol,
27(3), 912-919.
Abstract:
Comparing pre- and post-copulatory mate competition using social network analysis in wild crickets.
Sexual selection results from variation in success at multiple stages in the mating process, including competition before and after mating. The relationship between these forms of competition, such as whether they trade-off or reinforce one another, influences the role of sexual selection in evolution. However, the relationship between these 2 forms of competition is rarely quantified in the wild. We used video cameras to observe competition among male field crickets and their matings in the wild. We characterized pre- and post-copulatory competition as 2 networks of competing individuals. Social network analysis then allowed us to determine 1) the effectiveness of precopulatory competition for avoiding postcopulatory competition, 2) the potential for divergent mating strategies, and 3) whether increased postcopulatory competition reduces the apparent reproductive benefits of male promiscuity. We found 1) limited effectiveness of precopulatory competition for avoiding postcopulatory competition; 2) males do not specifically engage in only 1 type of competition; and 3) promiscuous individuals tend to mate with each other, which will tend to reduce variance in reproductive success in the population and highlights the trade-off inherent in mate guarding. Our results provide novel insights into the works of sexual competition in the wild. Furthermore, our study demonstrates the utility of using network analyses to study competitive interactions, even in species lacking obvious social structure.
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Author URL.
Hopwood PE, Moore AJ, Tregenza T, Royle NJ (2016). Erratum to Male burying beetles extend, not reduce, parental care duration when reproductive competition is high [J. Evol. Biol. 28: 1394-1402]. Journal of Evolutionary Biology, 29(1).
Lane SM, Haughan AE, Evans D, Tregenza T, House CM (2016). Same-sex sexual behaviour as a dominance display.
Animal Behaviour,
114, 113-118.
Abstract:
Same-sex sexual behaviour as a dominance display
Same-sex sexual behaviour (SSB) is widespread across taxa. One adaptive hypothesis to explain the occurrence and maintenance of SSB is that it acts to intensify or diminish aggression by providing males with a means to reinforce or resolve dominance. However, evidence for this hypothesis is very limited across taxa and the possibility that SSB acts as an extension of intrasexual competition remains contentious. We investigated the role of SSB in intensifying or diminishing aggression in the broad-horned flour beetle, Gnatocerus cornutus. We tested the hypothesis that SSB is an extension of male-male competition by observing how the occurrence of SSB and the stability of SSB courtship roles (i.e. whether males switched between mounting and being mounted) influenced levels of aggression within pairs. We found that, typically, males rapidly establish fixed SSB roles and moreover that the occurrence of SSB and the stability of SSB roles had a highly significant effect on levels of aggression observed within pairs. Pairs in which one male consistently mounted the other showed significantly lower levels of aggression than pairs in which neither male exhibited SSB or in which males continuously switched SSB roles and attempted to mount each other. Furthermore, males that were consistently on the receiving end of SSB demonstrated lower propensity to court females and had a lower mating success than active males. This pattern was analogous to that found in loser males as a result of fighting. Males that lost fights also courted less and had lower mating success than males that won fights. Our findings provide the first empirical support for the hypothesis that SSB is an extension of male-male competition. Furthermore, our results suggest that SSB may act as a display, allowing males to resolve dominance hierarchies without escalating into an injurious fight.
Abstract.
Lane SM, Dickinson AW, Tregenza T, House CM (2016). Sexual Selection on male cuticular hydrocarbons via male–male competition and female choice.
Journal of Evolutionary Biology,
29(7), 1346-1355.
Abstract:
Sexual Selection on male cuticular hydrocarbons via male–male competition and female choice
AbstractTraditional views of sexual selection assumed that male–male competition and female mate choice work in harmony, selecting upon the same traits in the same direction. However, we now know that this is not always the case and that these two mechanisms often impose conflicting selection on male sexual traits. Cuticular hydrocarbons (CHCs) have been shown to be linked to both social dominance and male attractiveness in several insect species. However, although several studies have estimated the strength and form of sexual selection imposed on male CHCs by female mate choice, none have established whether these chemical traits are also subject to sexual selection via male–male competition. Using a multivariate selection analysis, we estimate and compare sexual selection exerted by male–male competition and female mate choice on male CHC composition in the broad‐horned flour beetle Gnatocerus cornutus. We show that male–male competition exerts strong linear selection on both overall CHC abundance and body size in males, while female mate choice exerts a mixture of linear and nonlinear selection, targeting not just the overall amount of CHCs expressed but the relative abundance of specific hydrocarbons as well. We discuss the potential implications of this antagonistic selection with regard to male reproductive success.
Abstract.
Hopwood PE, Moore AJ, Tregenza T, Royle NJ (2016). The effect of size and sex ratio experiences on reproductive competition in <i>Nicrophorus vespilloides</i> burying beetles in the wild.
Journal of Evolutionary Biology,
29(3), 541-550.
Abstract:
The effect of size and sex ratio experiences on reproductive competition in Nicrophorus vespilloides burying beetles in the wild
AbstractMale parents face a choice: should they invest more in caring for offspring or in attempting to mate with other females? the most profitable course depends on the intensity of competition for mates, which is likely to vary with the population sex ratio. However, the balance of pay‐offs may vary among individual males depending on their competitive prowess or attractiveness. We tested the prediction that sex ratio and size of the resource holding male provide cues regarding the level of mating competition prior to breeding and therefore influence the duration of a male's biparental caring in association with a female. Male burying beetles, Nicrophorus vespilloides were reared, post‐eclosion, in groups that differed in sex ratio. Experimental males were subsequently translocated to the wild, provided with a breeding resource (carcass) and filmed. We found no evidence that sex ratio cues prior to breeding affected future parental care behaviour but males that experienced male‐biased sex ratios took longer to attract wild mating partners. Smaller males attracted a higher proportion of females than did larger males, securing significantly more monogamous breeding associations as a result. Smaller males thus avoided competitive male–male encounters more often than larger males. This has potential benefits for their female partners who avoid both intrasexual competition and direct costs of higher mating frequency associated with competing males.
Abstract.
Fisher DN, Rodríguez-Muñoz R, Tregenza T (2016). Wild cricket social networks show stability across generations. BMC Evolutionary Biology, 16(1).
Fisher DN, James A, Rodríguez-Muñoz R, Tregenza T (2015). Behaviour in captivity predicts some aspects of natural behaviour, but not others, in a wild cricket population.
Proc Biol Sci,
282(1809).
Abstract:
Behaviour in captivity predicts some aspects of natural behaviour, but not others, in a wild cricket population.
Examining the relevance of 'animal personality' involves linking consistent among- and within-individual behavioural variation to fitness in the wild. Studies aiming to do this typically assay personality in captivity and rely on the assumption that measures of traits in the laboratory reflect their expression in nature. We examined this rarely tested assumption by comparing laboratory and field measurements of the behaviour of wild field crickets (Gryllus campestris) by continuously monitoring individual behaviour in nature, and repeatedly capturing the same individuals and measuring their behaviour in captivity. We focused on three traits that are frequently examined in personality studies: shyness, activity and exploration. All of them showed repeatability in the laboratory. Laboratory activity and exploration predicted the expression of their equivalent behaviours in the wild, but shyness did not. Traits in the wild were predictably influenced by environmental factors such as temperature and sunlight, but only activity showed appreciable within-individual repeatability. This suggests that some behaviours typically studied as personality traits can be accurately assayed in captivity, but the expression of others may be highly context-specific. Our results highlight the importance of validating the relevance of laboratory behavioural assays to analogous traits measured in the wild.
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Author URL.
Tyler F, Fisher D, d'Ettorre P, Rodríguez-Muñoz R, Tregenza T (2015). Chemical cues mediate species recognition in field crickets.
Frontiers in Ecology and Evolution,
3(MAY).
Abstract:
Chemical cues mediate species recognition in field crickets
Cuticular hydrocarbons (CHCs) are important in mate choice in many insects, and may be used for species recognition if CHC profiles differ between potentially hybridizing species. In the sibling field cricket species Gryllus campestris and G. bimaculatus, females of G. bimaculatus are tolerant toward G. campestris males and can mate with them. However, G. campestris females are highly aggressive toward heterospecific G. bimaculatus males, and matings between them never happen. We examined whether cricket females might use CHCs to determine the species identity of their potential mates. We firstly analyzed the cuticular chemical profile by gas chromatography and mass spectrometry to assess the potential of CHCs to be used for species recognition in these crickets. We then manipulated females' ability to detect chemical cues by carrying out chemical ablation of the antennae, and measured changes in aggressive responses to heterospecific males. We show that there are significant interspecies differences in CHC expression for both sexes, and that females with chemically ablated antennae reduce aggressive behavior toward heterospecific males. Our findings support the prediction that cuticular semiochemicals can play a key role in reproductive isolation between closely related insect species.
Abstract.
Fisher DN, David M, Tregenza T, Rodríguez-Muñoz R (2015). Dynamics of among-individual behavioral variation over adult lifespan in a wild insect.
Behav Ecol,
26(4), 975-985.
Abstract:
Dynamics of among-individual behavioral variation over adult lifespan in a wild insect.
Investigating patterns of among and within-individual trait variation in populations is essential to understanding how selection shapes phenotypes. Behavior is often the most flexible aspect of the phenotype, and to understand how it is affected by selection, we need to examine how consistent individuals are. However, it is not well understood whether among-individual differences tend to remain consistent over lifetimes, or whether the behavior of individuals relative to one another varies over time. We examined the dynamics of 4 behavioral traits (tendency to leave a refuge, shyness, activity, and exploration) in a wild population of field crickets (Gryllus campestris). We tagged individuals and then temporarily removed them from their natural environment and tested them under laboratory conditions. All 4 traits showed among-individual variance in mean levels of expression across the adult lifespan, but no significant differences in how rapidly expression changed with age. For all traits, among-individual variance increased as individuals got older. Our findings reveal seldom examined changes in variance components over the adult lifetime of wild individuals. Such changes will have important implications for the relationship between behavioral traits, life-histories, and fitness and the consequences of selection on wild individuals.
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Author URL.
Hopwood PE, Moore AJ, Tregenza T, Royle NJ (2015). Male burying beetles extend, not reduce, parental care duration when reproductive competition is high.
J Evol Biol,
28(7), 1394-1402.
Abstract:
Male burying beetles extend, not reduce, parental care duration when reproductive competition is high.
Male parents spend less time caring than females in many species with biparental care. The traditional explanation for this pattern is that males have lower confidence of parentage, so they desert earlier in favour of pursuing other mating opportunities. However, one recent alternative hypothesis is that prolonged male parental care might also evolve if staying to care actively improves paternity. If this is the case, an increase in reproductive competition should be associated with increased paternal care. To test this prediction, we manipulated the level of reproductive competition experienced by burying beetles, Nicrophorus vespilloides (Herbst, 1783). We found that caregiving males stayed for longer and mated more frequently with their partner when reproductive competition was greater. Reproductive productivity did not increase when males extended care. Our findings provide support for the increased paternity hypothesis. Extended duration of parental care may be a male tactic both protecting investment (in the current brood) and maximizing paternity (in subsequent brood(s) via female stored sperm) even if this fails to maximize current reproductive productivity and creates conflict of interest with their mate via costs associated with increased mating frequency.
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Author URL.
HOPWOOD PE, MOORE AJ, TREGENZA TOM, ROYLE NJ (2015). Niche variation and the maintenance of variation in body size in a burying beetle.
Ecological Entomology,
41(1), 96-104.
Abstract:
Niche variation and the maintenance of variation in body size in a burying beetle
1. In burying beetles (Nicrophorinae), body size is known to provide both a fecundity advantage (in females) and successful resource defence (in males and females). Despite this, considerable variation in body sizes is observed in natural populations.2. A possible explanation for the maintenance of this variation, even with intra‐ and inter‐specific resource competition, is that individuals might assort according to body size on different‐sized breeding resources.3. We tested prediction that ‘bigger is always better’, in the wild. and in the laboratory, by experimentally manipulating combinations of available breeding‐resource size (mouse carcasses) and competitor's body size in Nicrophorus vespilloides (Herbst 1783).4. In the field, large female beetles deserted small carcasses, without breeding, more often than they did larger carcasses, but small females used carcasses indiscriminately with respect to size. In the laboratory, large beetles reared larger broods (with more offspring) on larger carcasses than small beetles, but on small carcasses small beetles had a reproductive advantage over large ones. Offspring size covaried with carcass size independently of parental body size.5. The present combined results suggest breeding resource value depends on an individual's body size, and variation in body size is environmentally induced: maintained by differences in available carcass sizes. This produces a mechanism by which individual specialisation leads to an increase in niche variation via body size in these beetles.
Abstract.
Pitchers W, Wolf JB, Tregenza T, Hunt J, Dworkin I (2014). Evolutionary rates for multivariate traits: the role of selection and genetic variation.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences,
369(1649).
Abstract:
Evolutionary rates for multivariate traits: the role of selection and genetic variation.
A fundamental question in evolutionary biology is the relative importance of selection and genetic architecture in determining evolutionary rates. Adaptive evolution can be described by the multivariate breeders' equation (Δz(-)=Gβ), which predicts evolutionary change for a suite of phenotypic traits (Δz(-)) as a product of directional selection acting on them (β) and the genetic variance-covariance matrix for those traits (G ). Despite being empirically challenging to estimate, there are enough published estimates of G and β to allow for synthesis of general patterns across species. We use published estimates to test the hypotheses that there are systematic differences in the rate of evolution among trait types, and that these differences are, in part, due to genetic architecture. We find some evidence that sexually selected traits exhibit faster rates of evolution compared with life-history or morphological traits. This difference does not appear to be related to stronger selection on sexually selected traits. Using numerous proposed approaches to quantifying the shape, size and structure of G, we examine how these parameters relate to one another, and how they vary among taxonomic and trait groupings. Despite considerable variation, they do not explain the observed differences in evolutionary rates.
Abstract.
Van Buskirk J, Krügel A, Kunz J, Miss F, Stamm A (2014). The Rate of Degradation of Chemical Cues Indicating Predation Risk: an Experiment and Review.
Ethology,
120(9), 942-949.
Abstract:
The Rate of Degradation of Chemical Cues Indicating Predation Risk: an Experiment and Review
AbstractMany prey taxa use kairomones or alarm pheromones to assess the risk of predation in aquatic environments, and the rate at which these cues attenuate determines how precisely they indicate the local density of predators. We estimated the rate of degradation of chemical cues generated by Aeshna dragonfly larvae feeding on Rana temporaria tadpoles. The half‐life of the cue was 35 h and was not influenced by whether it was aged in pond water or tap water or whether other tadpoles were present in the container in which cue‐aging occurred. A review of other published estimates of predator cue half‐life revealed values of 0.2–126 h, and variation among studies was unrelated to the type of aging water, the venue in which water was aged or prey behavior observed (laboratory, field), or the type of behavior that was recorded. We conclude that factors affecting the persistence of predator cues remain uncertain in spite of their importance for understanding the evolution of induced defenses.
Abstract.
Silk MJ, Croft DP, Tregenza T, Bearhop S (2014). The importance of fission-fusion social group dynamics in birds.
IBIS,
156(4), 701-715.
Author URL.
Pitchers WR, Klingenberg CP, Tregenza T, Hunt J, Dworkin I (2014). The potential influence of morphology on the evolutionary divergence of an acoustic signal.
J Evol Biol,
27(10), 2163-2176.
Abstract:
The potential influence of morphology on the evolutionary divergence of an acoustic signal.
The evolution of acoustic behaviour and that of the morphological traits mediating its production are often coupled. Lack of variation in the underlying morphology of signalling traits has the potential to constrain signal evolution. This relationship is particularly likely in field crickets, where males produce acoustic advertisement signals to attract females by stridulating with specialized structures on their forewings. In this study, we characterize the size and geometric shape of the forewings of males from six allopatric populations of the black field cricket (Teleogryllus commodus) known to have divergent advertisement calls. We sample from each of these populations using both wild-caught and common-garden-reared cohorts, allowing us to test for multivariate relationships between wing morphology and call structure. We show that the allometry of shape has diverged across populations. However, there was a surprisingly small amount of covariation between wing shape and call structure within populations. Given the importance of male size for sexual selection in crickets, the divergence we observe among populations has the potential to influence the evolution of advertisement calls in this species.
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Author URL.
Neenan STV, Hodgson DJ, Tregenza T, Boothroyd D, Ellis CD (2014). The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus).
Aquaculture ResearchAbstract:
The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus)
Assessments of stock enhancement programmes for European lobsters (Homarus gammarus) require mark-recapture analysis of stocked individuals. However, established tag technology is deemed unsuitable for extensive use by many current lobster hatcheries, particularly upon the early juvenile stages. We tested the suitability of fluorescent Visible Implant Elastomer (VIE) tags for use in 5-month-old juvenile lobsters. Three treatment groups comprising 348 cultured lobsters in total were used to examine survival, growth and tag retention, and to assess mobility, shelter use and moulting behaviours. Tagging had no significant effect on lobster survival, growth, mobility, shelter use or moult frequency. Survival over 7 weeks was 75% among lobsters tagged with two elastomers, 76% in those with one elastomer and 74% among untagged controls. Mortality during moulting did not increase in tagged (6%) compared to untagged lobsters (9%). We found no evidence that VIE tags cause any negative effects that would be expected to inhibit survival upon wild release, but tag loss had reached 12% in both tagged treatments after 7 weeks and showed no sign of abating. Our study suggests that VIEs effectiveness in discerning cultured lobsters long after wild release may be limited when used in smaller juveniles. © 2014 John Wiley & Sons Ltd.
Abstract.
Veen T, Faulks J, Tyler F, Lloyd J, Tregenza T (2013). Diverse reproductive barriers in hybridising crickets suggests extensive variation in the evolution and maintenance of isolation.
Evolutionary Ecology,
27(5), 993-1015.
Abstract:
Diverse reproductive barriers in hybridising crickets suggests extensive variation in the evolution and maintenance of isolation
Reproductive barriers reduce gene flow between populations and maintain species identities. A diversity of barriers exist, acting before, during and after mating. To understand speciation and coexistence, these barriers need to be quantified and their potential interactions revealed. We use the hybridising field crickets Gryllus bimaculatus and G. campestris as a model to understand the full compliment and relative strength of reproductive barriers. We find that males of both species prefer conspecific females, but the effect is probably too weak to represent a barrier. In contrast, prezygotic barriers caused by females being more attracted to conspecific male song and preferentially mounting and mating with conspecifics are strong and asymmetric. Postzygotic barriers vary in direction; reductions in fecundity and egg viability create selection against hybridisation, but hybrids live longer than pure-bred individuals. Hybrid females show a strong preference for G. bimaculatus songs, which together with a complete lack of hybridisation by G. campestris females, suggests that asymmetric gene flow is likely. For comparison, we review reproductive barriers that have been identified between other Gryllids and conclude that multiple barriers are common. Different species pairs are separated by qualitatively different combinations of barriers, suggesting that reproductive isolation and even the process of speciation itself may vary widely even within closely related groups. © 2012 Springer Science+Business Media Dordrecht.
Abstract.
Harrison XA, Hodgson DJ, Inger R, Colhoun K, Gudmundsson GA, McElwaine G, Tregenza T, Bearhop S (2013). Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
PLoS One,
8(10).
Abstract:
Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
In many animals, processes occurring in one season carry over to influence reproductive success and survival in future seasons. The strength of such carry-over effects is unlikely to be uniform across years, yet our understanding of the processes that are capable of modifying their strength remains limited. Here we show that female light-bellied Brent geese with higher body mass prior to spring migration successfully reared more offspring during breeding, but only in years where environmental conditions during breeding were favourable. In years of bad weather during breeding, all birds suffered reduced reproductive output irrespective of pre-migration mass. Our results suggest that the magnitude of reproductive benefits gained by maximising body stores to fuel breeding fluctuates markedly among years in concert with conditions during the breeding season, as does the degree to which carry-over effects are capable of driving variance in reproductive success among individuals. Therefore while carry-over effects have considerable power to drive fitness asymmetries among individuals, our ability to interpret these effects in terms of their implications for population dynamics is dependent on knowledge of fitness determinants occurring in subsequent seasons.
Abstract.
Author URL.
Tyler F, Rodríguez-Muñoz R, Tregenza T (2013). Fertilisation and early developmental barriers to hybridisation in field crickets.
BMC Evol Biol,
13Abstract:
Fertilisation and early developmental barriers to hybridisation in field crickets.
BACKGROUND: Post-mating interactions between the reproductive traits and gametes of mating individuals and among their genes within zygotes are invariably complex, providing multiple opportunities for reproduction to go awry. These interactions have the potential to act as barriers to gene flow between species, and may be important in the process of speciation. There are multiple post-mating barriers to interbreeding between the hybridising field crickets Gryllus bimaculatus and G. campestris. Female G. bimaculatus preferentially store sperm from conspecific males when mated to both conspecific and heterospecific partners. Additionally, conspecific males sire an even greater proportion of offspring than would be predicted from their sperm's representation in the spermatheca. The nature of these post-sperm-storage barriers to hybridisation are unknown. We use a fluorescent staining technique to determine whether barriers occur prior to, or during embryo development. RESULTS: We show that eggs laid by G. bimaculatus females mated to G. campestris males are less likely to begin embryogenesis than eggs from conspecific mating pairs. of the eggs that are successfully fertilised and start to develop, those from heterospecific mating pairs are more likely to arrest early, prior to blastoderm formation. We find evidence for bimodal variation among egg clutches in the number of developing embryos that subsequently arrest, indicating that there is genetic variation for incompatibility between mating individuals. In contrast to the pattern of early embryonic mortality, those hybrids reaching advanced stages of embryogenesis have survival rates equal to that of embryos from conspecific mating pairs. CONCLUSIONS: Post-sperm-storage barriers to hybridisation show evidence of genetic polymorphism. They are sufficiently large, that if the species interbreed where they are sympatric, these barriers could play a role in the maintenance of reproductive isolation between them. The number of eggs that fail to develop represents a substantial cost of hybridization to G. bimaculatus females, and this cost could reinforce the evolution of barriers occurring earlier in the reproductive process.
Abstract.
Author URL.
Pitchers WR, Brooks R, Jennions MD, Tregenza T, Dworkin I, Hunt J (2013). Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
Journal of Evolutionary Biology,
26(5), 1060-1078.
Abstract:
Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus
Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders' equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance-covariance matrix (P) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild-caught crickets from each of the populations and then a second subset after rearing crickets under common-garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high- and low-nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit. © 2013 the Authors. © 2013 European Society for Evolutionary Biology.
Abstract.
Brooks R, Pitchers WR, Jennions MD, Tregenza T, Dworkin I, Hunt J (2013). Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
J Evol Biol,
26(5), 1060-1078.
Abstract:
Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders' equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance-covariance matrix (P) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild-caught crickets from each of the populations and then a second subset after rearing crickets under common-garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high- and low-nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit.
Abstract.
Author URL.
Tyler F, Harrison XA, Bretman A, Veen T, Rodríguez-Muñoz R, Tregenza T (2013). Multiple post-mating barriers to hybridization in field crickets.
Molecular Ecology,
22(6), 1640-1649.
Abstract:
Multiple post-mating barriers to hybridization in field crickets
Mechanisms that prevent different species from interbreeding are fundamental to the maintenance of biodiversity. Barriers to interspecific matings, such as failure to recognize a potential mate, are often relatively easy to identify. Those occurring after mating, such as differences in the how successful sperm are in competition for fertilisations, are cryptic and have the potential to create selection on females to mate multiply as a defence against maladaptive hybridization. Cryptic advantages to conspecific sperm may be very widespread and have been identified based on the observations of higher paternity of conspecifics in several species. However, a relationship between the fate of sperm from two species within the female and paternity has never been demonstrated. We use competitive microsatellite PCR to show that in two hybridising cricket species, Gryllus bimaculatus and G. campestris, sequential cryptic reproductive barriers are present. In competition with heterospecifics, more sperm from conspecific males is stored by females. Additionally, sperm from conspecific males has a higher fertilisation probability. This reveals that conspecific sperm precedence can occur through processes fundamentally under the control of females, providing avenues for females to evolve multiple mating as a defence against hybridization, with the counterintuitive outcome that promiscuity reinforces isolation and may promote speciation. © 2013 Blackwell Publishing Ltd.
Abstract.
Tyler F, Harrison XA, Bretman A, Veen T, Rodríguez-Muñoz R, Tregenza T (2013). Multiple post-mating barriers to hybridization in field crickets.
Mol Ecol,
22(6), 1640-1649.
Abstract:
Multiple post-mating barriers to hybridization in field crickets.
Mechanisms that prevent different species from interbreeding are fundamental to the maintenance of biodiversity. Barriers to interspecific matings, such as failure to recognize a potential mate, are often relatively easy to identify. Those occurring after mating, such as differences in the how successful sperm are in competition for fertilisations, are cryptic and have the potential to create selection on females to mate multiply as a defence against maladaptive hybridization. Cryptic advantages to conspecific sperm may be very widespread and have been identified based on the observations of higher paternity of conspecifics in several species. However, a relationship between the fate of sperm from two species within the female and paternity has never been demonstrated. We use competitive microsatellite PCR to show that in two hybridising cricket species, Gryllus bimaculatus and G. campestris, sequential cryptic reproductive barriers are present. In competition with heterospecifics, more sperm from conspecific males is stored by females. Additionally, sperm from conspecific males has a higher fertilisation probability. This reveals that conspecific sperm precedence can occur through processes fundamentally under the control of females, providing avenues for females to evolve multiple mating as a defence against hybridization, with the counterintuitive outcome that promiscuity reinforces isolation and may promote speciation.
Abstract.
Author URL.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2013). No benefits of polyandry to female green turtles.
Behavioral Ecology,
24(4), 1022-1029.
Abstract:
No benefits of polyandry to female green turtles
Multiple paternity is extremely common in natural populations of almost all reptiles studied to date, suggesting that pay-offs from polyandrous mating systems are important in these taxonomic groups. However, strong evidence in support of direct or indirect benefits to females is scarce. We examined the relationship between polyandry and components of female reproductive success and offspring fitness in the promiscuous green turtle (Chelonia mydas), a species that exhibits highly variable levels of multiple paternity. We did not detect any clear fitness benefits to polyandrous females in this study, and we discuss the potential of sexual conflict to influence female mating patterns in marine turtles. We show that polyandrous females produce significantly smaller clutches than monandrous females, highlighting a potential cost to polyandry in green turtles. Furthermore, multiple paternity was more common in returning females (recorded breeding in a previous season) than in females nesting for the first time at our study site, possibly reflecting increased encounter rates with males or sperm storage across breeding seasons. Our results reveal potentially complex influences of female traits, environment, and mating strategy on components of reproductive success, and we discuss the challenges associated with unraveling the costs and benefits of multiple mating in natural populations. © 2013 the Author. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.
Abstract.
Attisano A, Tregenza T, Moore AJ, Moore PJ (2013). Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciatus. Animal Behaviour
Attisano A, Tregenza T, Moore AJ, Moore PJ (2013). Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciatus.
Animal Behaviour,
86(3), 651-657.
Abstract:
Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciatus
Migration evolves as a response to seasonally unfavourable environments but plasticity in reproductive physiology is another avenue by which insects can respond to resource-poor conditions. We investigated the relationship between individual variation in migratory propensity and the level of response to poor conditions modulated by the female reproductive physiology. We tested the hypothesis that, compared to migrants, residential behaviour is associated with a higher degree of phenotypic plasticity in oosorption, an adaptive physiological mechanism that allows females to recoup resources from undeveloped oocytes. Reallocation from reproduction to survival would allow females to skip migration and to cope with unfavourable environments. If this plasticity is evolved, we further predicted it would vary between as well as within populations. We examined variation associated with migratory behaviour in females from four populations of the milkweed bug, Oncopeltus fasciatus, using a behavioural assay to categorize females as either migrant or resident and observing the differences in oosorption between these groups. As expected, food availability, source population and wing length influenced the propensity for migratory flight, and food availability influenced levels of oosorption. We also found support for our key prediction that resident females are characterized by higher levels of ovarian oosorption than migrant females. Our study provides support for a physiological difference between migrant and resident females and suggests the presence of both physiological and behavioural tactics that interact with the potential for migration to provide adaptation to seasonally challenging environments. © 2013 the Association for the Study of Animal Behaviour.
Abstract.
Pincheira-Donoso D, Tregenza T, Witt MJ, Hodgson DJ (2013). The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac. Global Ecology and Biogeography
Pincheira-Donoso D, Tregenza T, Witt MJ, Hodgson DJ (2013). The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac.
Global Ecology and Biogeography,
22(7), 857-867.
Abstract:
The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac
Aim: Evolutionary radiations into novel areas or niches require innovative adaptations. However, rapid subsequent changes in these novel conditions might demand rapid re-adaptations to secure population persistence and prevent extinction. We propose that reptilian viviparity (live birth) is consistent with such a scenario. Using the Liolaemus lizard radiation, we investigate the hypotheses that historical invasions of cold climates have been permitted by transitions to viviparity, and that this parity mode is irreversible. Then, we investigate whether these combined factors restrict viviparous lizards to cold climates, and hence, whether viviparous species are particularly threatened by climate change. Location: South America. Methods: We employ phylogenetic analyses to investigate evolutionary transitions in reproductive modes and their consequences for environmental restrictions in viviparous lizards. We then employ climatic projections to predict the impact of climate change on the future persistence of these organisms. Results: the oviparity-to-viviparity transition is consistently associated with colonization of cold climates, and appears to be irreversible. Since viviparity seems less viable (compared with oviparity) in warm climates, species that evolve viviparity in cold climates are likely to remain adaptively constrained to such environments. Therefore, upward-poleward advances of climate warming will cause severe shifts and contractions of viviparous species ranges, threatening major extinctions over the next half century. Main conclusions: Viviparity has been largely responsible for the successful radiation of Liolaemus into cold climates, but since this adaptation is predominantly viable in these environments and is unlikely to re-evolve into oviparity, viviparity may prove to be an evolutionary dead-end for lizards facing rapid climate change. © 2013 John Wiley & Sons Ltd.
Abstract.
Tyler F, Tregenza T (2013). Why do so many flour beetle copulations fail?.
Entomologia Experimentalis et Applicata,
146(1), 199-206.
Abstract:
Why do so many flour beetle copulations fail?
Copulations that fail to result in fertilisations are common across a broad range of species, and remain enigmatic given the inherent costs that are being paid by both partners. The determinants of failures are varied and can take effect before, during, or after copulating. In the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), population estimates of copulations failing to result in fertilisations as high as 55% have been reported, suggesting that the causes of these failures play an important role in the mating system, or that the costs experienced by those determining failure, in this system likely the females, is low. Here, we show that failure is determined peri-copulation; successful spermatophore transfer (indicated by change in mass of mating individuals) typically results in offspring production, suggesting that mechanisms of post-copulatory female choice do not cause outright failure. The proportion of copulations that failed to result in fertilisations was apparently not influenced by the relatedness of mating pairs, the age, mating status, or mass of the female, or the interval she experienced between matings. This suggests that alternative adaptive explanations are responsible for the prevalence of copulations that fail to result in fertilisations in this species, or that the costs involved are sufficiently small, so that selection against such failures is weak. © 2012 the Authors Entomologia Experimentalis et Applicata © 2012 the Netherlands Entomological Society.
Abstract.
Veen T, Faulks J, Tyler F, Lloyd J, Tregenza T (2012). Diverse reproductive barriers in hybridising crickets suggests extensive variation in the evolution and maintenance of isolation. Evolutionary Ecology, 1-23.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2012). Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
Molecular Ecology,
21(14), 3625-3635.
Abstract:
Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1 year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult. © 2012 Blackwell Publishing Ltd.
Abstract.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2012). Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
Mol Ecol,
21(14), 3625-3635.
Abstract:
Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult.
Abstract.
Author URL.
Sharma MD, Griffin RM, Hollis J, Tregenza T, Hosken DJ (2012). Reinvestigating good genes benefits of mate choice in Drosophila simulans.
Biological Journal of the Linnean Society,
106(2), 295-306.
Abstract:
Reinvestigating good genes benefits of mate choice in Drosophila simulans
Studies investigating the genetic benefits of female mate choice frequently find Fisherian benefits to choice, at the same time as detecting small or no good genes (viability) effects. This could be because sons trade-off viability for increased mating success and, accordingly, it has been suggested that good genes benefits should be investigated in daughters. However, good genes benefits via daughters could also be disrupted by intralocus sexual conflict. As a result, it is not clear when and if good genes benefits should accrue. We investigated potential good genes effects in Drosophila simulans using an isofemale line approach. We assessed the attractiveness of males in two different ways and then measured the longevity, as well as lifetime reproductive success, of their daughters. We also assessed potential direct benefits of female mate choice and good genes effects through the longevity of sons. We found no evidence of direct or good genes benefits to females mating with attractive males, and the failure to find good genes effects via daughters was apparently not a result of masking through intralocus sexual conflict. The results obtained in the present study are consistent with previous findings in this species, and suggest that good genes benefits are at best very small in our study population. © 2012 the Linnean Society of London.
Abstract.
Sharma MD, Mitchell C, Hunt J, Tregenza T, Hosken DJ (2012). The genetics of cuticular hydrocarbon profiles in the Fruit Fly Drosophila simulans.
J Hered,
103(2), 230-239.
Abstract:
The genetics of cuticular hydrocarbon profiles in the Fruit Fly Drosophila simulans.
Female mate choice is one mechanism of sexual selection and, provided there is adequate genetic variation in the male traits that are the target of this selection, they will evolve via female choice. Cuticular hydrocarbons (CHCs) are important in Drosophila mate choice, but relatively little is known about the underlying genetic architecture of CHC profiles in Drosophila simulans. Here, we used gas chromatography-mass spectrometry to investigate patterns of genetic variation in the CHC profiles of male and female D. simulans using isofemale lines. We found substantial genetic variation for CHC profiles and individual CHC components, and individual CHCs were frequently strongly genetically correlated, with a tendency for negative covariance between long- and short-chain CHCs in males. Intersexual genetic covariances were often weak and frequently differed in sign. These findings are novel and significant, highlighting the previously unexplored genetic architecture of CHCs in D. simulans and suggest that this architecture may facilitate sex-specific CHC evolution.
Abstract.
Author URL.
Wright LI, Stokes KL, Fuller WJ, Godley BJ, McGowan A, Snape R, Tregenza T, Broderick AC (2012). Turtle mating patterns buffer against disruptive effects of climate change.
Proc Biol Sci,
279(1736), 2122-2127.
Abstract:
Turtle mating patterns buffer against disruptive effects of climate change.
For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2-4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.
Abstract.
Author URL.
Tyler F, Tregenza T (2012). Why do so many flour beetle copulations fail. Entomologia Experimentalis et Applicata
Pincheira-Donoso D, Tregenza T (2011). Fecundity Selection and the Evolution of Reproductive Output and Sex-Specific Body Size in the Liolaemus Lizard Adaptive Radiation.
Evolutionary Biology,
38(2), 197-207.
Abstract:
Fecundity Selection and the Evolution of Reproductive Output and Sex-Specific Body Size in the Liolaemus Lizard Adaptive Radiation
Fecundity is a primary component of fitness. Theory predicts that the evolution of fecundity through increased brood size results from fecundity selection favouring larger female size to accommodate more offspring and to store more energy. This is expected to generate asymmetric selection on body size between the sexes, ultimately driving evolution of female-biased sexual size dimorphism. Additionally, it has been predicted that the intensity of fecundity selection increases when the opportunities for reproduction are reduced by the limiting thermal effects of increasing latitude-elevation (i.e. decreasing environmental temperatures) on the length of the reproductive season. This later factor would be particularly strong among ectotherms, where reproduction is heavily temperature-dependent. However, this integrative perspective on reproductive evolution by fecundity selection has rarely been investigated. Here, we employ a comparative approach to investigate these predictions in Liolaemus, a prominent lizard radiation. As expected, Liolaemus reproductive output (i. e. offspring number per reproductive episode) increases predictably with increasing female size. However, contrary to predictions, we found that increased fecundity does not translate into female-biased SSD, and that combined latitude-elevation does not impose a detectable effect on fecundity. Finally, our allometric analyses reveal that SSD scales with body size, which supports the occurrence of Rensch's rule in these lizards. We discuss the evolutionary implications of our results, and the assumptions of the investigated hypotheses. © 2011 Springer Science+Business Media, LLC.
Abstract.
Bretman A, Rodríguez-Muñoz R, Walling C, Slate J, Tregenza T (2011). Fine-scale population structure, inbreeding risk and avoidance in a wild insect population.
Mol Ecol,
20(14), 3045-3055.
Abstract:
Fine-scale population structure, inbreeding risk and avoidance in a wild insect population.
The ecological and evolutionary importance of fine-scale genetic structure within populations is increasingly appreciated. However, available data are largely restricted to wild vertebrates and eusocial insects. In addition, there is the expectation that most insects tend to have such large- and high-density populations and are so mobile that they are unlikely to face inbreeding risks through fine-scale population structuring. This has made the growing body of evidence for inbreeding avoidance in insects and its implication in mating systems evolution somewhat enigmatic. We present a 4-year study of a natural population of field crickets. Using detailed video monitoring combined with genotyping, we track the movement of all adults within the population and investigate genetic structure at a fine scale. We find some evidence for relatives being found in closer proximity, both across generations and within a single breeding season. Whilst incestuous matings are not avoided, population inbreeding is low, suggesting that mating is close to random and the limited fine-scale structure does not create significant inbreeding risk. Hence, there is little evidence for selective pressures associated with the evolution of inbreeding avoidance mechanisms in a closely related species.
Abstract.
Author URL.
Rodríguez-Muñoz R, Bretman A, Tregenza T (2011). Guarding males protect females from predation in a wild insect.
Curr Biol,
21(20), 1716-1719.
Abstract:
Guarding males protect females from predation in a wild insect.
Males frequently remain in close proximity to their mate immediately postcopulation. This behavior has generally been interpreted as a guarding tactic designed to reduce the likelihood that a rival male can rapidly displace the ejaculate of the guarding male [1, 2]. Such attempts by males to control their mates represent a potential source of conflict [3-5], but guarding behaviors in species where it is difficult for males to control their mates suggest that conflict is not inevitable [6, 7]. We employed a network of infrared video cameras to study a wild population of individually marked and genotyped field crickets (Gryllus campestris). Lone females or males suffer similar rates of predation, but when a pair is attacked, the male allows the female priority access to their burrow, and in doing so dramatically increases his probability of being killed. In compensation for this increased predation risk, paired males mate more frequently and father more of the female's offspring. By staying with a male, females increase the sperm contribution of preferred males as well as reducing their predation risk. In contrast to conclusions based on previous lab studies, our field study suggests that mate guarding can evolve in a context of cooperation rather than conflict between the sexes.
Abstract.
Author URL.
HARRISON XA, BEARHOP S, INGER R, COLHOUN K, GUDMUNDSSON GA, HODGSON D, McELWAINE GRAHAM, TREGENZA TOM (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects. Molecular Ecology, 20(22), 4786-4795.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson D, McElwaine G, Tregenza T (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Molecular ecology,
20(22), 4786-4795.
Abstract:
Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Studies in a multitude of taxa have described a correlation between heterozygosity and fitness and usually conclude that this is evidence for inbreeding depression. Here, we have used multilocus heterozygosity (MLH) estimates from 15 microsatellite markers to show evidence of heterozygosity-fitness correlations (HFCs) in a long-distance migratory bird, the light-bellied Brent goose. We found significant, positive heterozygosity-heterozygosity correlations between random subsets of the markers we employed, and no evidence that a model containing all loci as individual predictors in a multiple regression explained significantly more variation than a model with MLH as a single predictor. Collectively, these results lend support to the hypothesis that the HFCs we have observed are a function of inbreeding depression. However, we do find that fitness correlations are only detectable in years where population-level productivity is high enough for the reproductive asymmetry between high and low heterozygosity individuals to become apparent. We suggest that lack of evidence of heterozygosity-fitness correlations in animal systems may be because heterozygosity is a poor proxy measure of inbreeding, especially when employing low numbers of markers, but alternatively because the asymmetries between individuals of different heterozygosities may only be apparent when environmental effects on fitness are less pronounced. © 2011 Blackwell Publishing Ltd.
Abstract.
Sinclair BJ, Bretman A, Tregenza T, Tomkins JL, Hosken DJ (2011). Metabolic rate does not decrease with starvation in Gryllus bimaculatus when changing fuel use is taken into account.
Physiological Entomology,
36(1), 84-89.
Abstract:
Metabolic rate does not decrease with starvation in Gryllus bimaculatus when changing fuel use is taken into account
Many behavioural traits are considered to be condition-dependent, reflecting the differential allocation of resources to fitness-related traits and maintenance, although the physiological underpinnings of condition dependence are not well understood. In the present study, the hypothesis that condition dependence in male Gryllus bimaculatus De Geer is mediated by a decrease in metabolic rate with declining condition is tested. CO2 production is measured by flow-through respirometry, with insect condition manipulated through starvation. Crickets starved for 7 days have lower CO2 emission rates than individuals starved for only 24 h. However, carbohydrate reserves are depleted in the first 3 days, suggesting that the initial metabolism is primarily fuelled by carbohydrate, with a shift to lipid stores after 3 days. If the metabolic rate is estimated using respiratory quotients reflecting this shift in fuels, there is no difference in metabolic rate between crickets starved for 24 h and 7 days, suggesting that metabolic rate does not decrease with declining condition. This implies that a decrease in metabolic rate during starvation may not be a general pattern in insects, and emphasizes the need to consider fuel use during metabolic rate estimation in starvation studies. © 2010 the Authors. Physiological Entomology © 2010 the Royal Entomological Society.
Abstract.
Veen T, Faulks J, Rodríguez-Muñoz R, Tregenza T (2011). Premating reproductive barriers between hybridising cricket species differing in their degree of polyandry.
PLoS One,
6(5).
Abstract:
Premating reproductive barriers between hybridising cricket species differing in their degree of polyandry.
Understanding speciation hinges on understanding how reproductive barriers arise between incompletely isolated populations. Despite their crucial role in speciation, prezygotic barriers are relatively poorly understood and hard to predict. We use two closely related cricket species, Gryllus bimaculatus and G. campestris, to experimentally investigate premating barriers during three sequential mate choice steps. Furthermore, we experimentally show a significant difference in polyandry levels between the two species and subsequently test the hypothesis that females of the more polyandrous species, G. bimaculatus, will be less discriminating against heterospecific males and hence hybridise more readily. During close-range mating behaviour experiments, males showed relatively weak species discrimination but females discriminated very strongly. In line with our predictions, this discrimination is asymmetric, with the more polyandrous G. bimaculatus mating heterospecifically and G. campestris females never mating heterospecifically. Our study shows clear differences in the strength of reproductive isolation during the mate choice process depending on sex and species, which may have important consequences for the evolution of reproductive barriers.
Abstract.
Author URL.
Sharma MD, Tregenza T, Hosken DJ (2011). Sex combs, allometry, and asymmetry in Drosophila.
Biological Journal of the Linnean Society,
103(4), 923-934.
Abstract:
Sex combs, allometry, and asymmetry in Drosophila
There has been recent debate about the expected allometry of sexually-selected traits. Although sexually-selected traits exhibit a diversity of allometric patterns, signalling characters are frequently positively allometric. By contrast, insect genitalia tend to be negatively allometric, although the allometry of nongenital sexually-selected characters in insects is largely unknown (with some notable exceptions). It has also been suggested that there should be a negative association between the asymmetry and size of bilaterally-paired, sexually-selected traits, although this claim is controversial. We assessed the allometry and asymmetry (fluctuating asymmetry, FA) of a nongenital contact-courtship structure, the sex comb, in replicate populations of three species of Drosophila (we also measured wing FA). Sex combs are sexually-selected characters used to grasp the female's abdomen and genitalia and to spread her wings prior to and during copulation. Although species differed in the size of the sex combs, all combs were positively allometric, and comb allometry did not generally differ significantly between species or populations. Comb and wing asymmetry did vary across species, although not across populations of the same species. However, FA was trait specific and was never negatively associated with trait size. © 2011 the Linnean Society of London.
Abstract.
Gay L, Hosken DJ, Eady P, Vasudev R, Tregenza T (2011). The evolution of harm--effect of sexual conflicts and population size.
Evolution,
65(3), 725-737.
Abstract:
The evolution of harm--effect of sexual conflicts and population size.
Conflicts of interest between mates can promote the evolution of male traits that reduce female fitness and that drive coevolution between the sexes. The rate of adaptation depends on the intensity of selection and its efficiency, which depends on drift and genetic variability. This leads to the largely untested prediction that coevolutionary adaptations such as those driven by sexual conflict should evolve faster in large populations. We tested this using the bruchid beetle Callosobruchus maculatus, a species where harm inflicted by males is well documented. Although most experimental evolution studies remove sexual conflict, we reintroduced it in populations in which it had been experimentally removed. Both population size and standing genetic variability were manipulated in a factorial experimental design. After 90 generations of relaxed conflict (monogamy), the reintroduction of sexual conflicts for 30 generations favored males that harmed females and females that were more resistant to the genital damage inflicted by males. Males evolved to become more harmful when population size was large rather than when initial genetic variation was enriched. Our study shows that sexual selection can create conditions in which males can benefit from harming females and that selection may tend to be more intense and effective in larger populations.
Abstract.
Author URL.
Gay L, Brown E, Tregenza T, Pincheira-Donoso D, Eady PE, Vasudev R, Hunt J, Hosken DJ (2011). The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus.
J Evol Biol,
24(2), 449-456.
Abstract:
The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus.
Males harm females during mating in a range of species. This harm is thought to evolve because it is directly or indirectly beneficial to the male, despite being costly to his mate. The resulting sexually antagonistic selection can cause sexual arms races. For sexually antagonistic co-evolution to occur, there must be genetic variation for traits involved in female harming and susceptibility to harm, but even then intersexual genetic correlations could facilitate or impede sexual co-evolution. Male Callosobruchus maculatus harm their mates during copulation by damaging the female's reproductive tract. However, there have been no investigations of the genetic variation in damage or in female susceptibility to damage, nor has the genetic covariance between these characters been assessed. Here, we use a full-sib/half-sib breeding design to show that male damage is heritable, whereas female susceptibility to damage is much less so. There is also a substantial positive genetic correlation between the two, suggesting that selection favouring damaging males will increase the prevalence of susceptible females. We also provide evidence consistent with intralocus sexual conflict in this species.
Abstract.
Author URL.
Lewis Z, Champion de Crespigny FE, Sait SM, Tregenza T, Wedell N (2011). Wolbachia infection lowers fertile sperm transfer in a moth.
Biol Lett,
7(2), 187-189.
Abstract:
Wolbachia infection lowers fertile sperm transfer in a moth.
The endosymbiotic bacterium Wolbachia pipientis manipulates host reproduction by rendering infected males reproductively incompatible with uninfected females (cytoplasmic incompatibility; CI). CI is believed to occur as a result of Wolbachia-induced modifications to sperm during maturation, which prevent infected sperm from initiating successful zygote development when fertilizing uninfected females' eggs. However, the mechanism by which CI occurs has been little studied outside the genus Drosophila. Here, we show that in the sperm heteromorphic Mediterranean flour moth, Ephestia kuehniella, infected males transfer fewer fertile sperm at mating than uninfected males. In contrast, non-fertile apyrene sperm are not affected. This indicates that Wolbachia may only affect fertile sperm production and highlights the potential of the Lepidoptera as a model for examining the mechanism by which Wolbachia induces CI in insects.
Abstract.
Author URL.
Harrison XA, Tregenza T, Inger R, Colhoun K, Dawson DA, Gudmundsson GA, Hodgson DJ, Horsburgh GJ, McElwaine G, Bearhop S, et al (2010). Cultural Inheritance Drives Site Fidelity and Migratory Connectivity in a Long Distance Migrant. Molecular Ecology, 19(24), 5484-5496.
Brown EA, Gay L, Vasudev R, Tregenza T, Eady PE, Hosken DJ (2010). Erratum: Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles (Heredity (2010) 105 (576) DOI:10.1038/hdy.2010.132). Heredity, 105(6).
Sharma MD, Tregenza T, Hosken DJ (2010). Female mate preferences in Drosophila simulans: evolution and costs.
J Evol Biol,
23(8), 1672-1679.
Abstract:
Female mate preferences in Drosophila simulans: evolution and costs.
Female mate preference is central to sexual selection, and all indirect benefit models require that there is genetic variation in female preference. This has rarely been tested however, with relatively few studies documenting heritable variation in female preference and even fewer that have directly selected on mate preference to unequivocally show that it can evolve. Additionally, costs of mate preference are poorly understood even though these have implications for preference evolution. We selected on female preference for ebony-males in replicate Drosophila simulans lines, and generated a rapid evolutionary response in both replicates, with the proportion of females mating with ebony-males increasing from approximately 5% to 30% after five generations of selection. This increase was independent of changes in ebony-males as only females were included in our selection regime. We could detect no cost to mate preference itself other than that associated with the fitness consequences of mating with ebony males.
Abstract.
Author URL.
Arnqvist G, Dowling DK, Eady P, Gay L, Tregenza T, Tuda M, Hosken DJ (2010). Genetic architecture of metabolic rate: environment specific epistasis between mitochondrial and nuclear genes in an insect.
Evolution,
64(12), 3354-3363.
Abstract:
Genetic architecture of metabolic rate: environment specific epistasis between mitochondrial and nuclear genes in an insect.
The extent to which mitochondrial DNA (mtDNA) variation is involved in adaptive evolutionary change is currently being reevaluated. In particular, emerging evidence suggests that mtDNA genes coevolve with the nuclear genes with which they interact to form the energy producing enzyme complexes in the mitochondria. This suggests that intergenomic epistasis between mitochondrial and nuclear genes may affect whole-organism metabolic phenotypes. Here, we use crossed combinations of mitochondrial and nuclear lineages of the seed beetle Callosobruchus maculatus and assay metabolic rate under two different temperature regimes. Metabolic rate was affected by an interaction between the mitochondrial and nuclear lineages and the temperature regime. Sequence data suggests that mitochondrial genetic variation has a role in determining the outcome of this interaction. Our genetic dissection of metabolic rate reveals a high level of complexity, encompassing genetic interactions over two genomes, and genotype × genotype × environment interactions. The evolutionary implications of these results are twofold. First, because metabolic rate is at the root of life histories, our results provide insights into the complexity of life-history evolution in general, and thermal adaptation in particular. Second, our results suggest a mechanism that could contribute to the maintenance of nonneutral mtDNA polymorphism.
Abstract.
Author URL.
Holwell GI, Winnick C, Tregenza T, Herberstein ME (2010). Genital shape correlates with sperm transfer success in the praying mantis Ciulfina klassi (Insecta: Mantodea).
Behavioral Ecology and Sociobiology,
64(4), 617-625.
Abstract:
Genital shape correlates with sperm transfer success in the praying mantis Ciulfina klassi (Insecta: Mantodea)
The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated. Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly, two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success. Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer. © 2009 Springer-Verlag.
Abstract.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T, Bearhop S (2010). Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources, 2, 365-371.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T, Bearhop S (2010). Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources, 1-7.
Rodríguez-Muñoz R, Bretman A, Slate J, Walling CA, Tregenza T (2010). Natural and sexual selection in a wild insect population.
Science,
328(5983), 1269-1272.
Abstract:
Natural and sexual selection in a wild insect population.
The understanding of natural and sexual selection requires both field and laboratory studies to exploit the advantages and avoid the disadvantages of each approach. However, studies have tended to be polarized among the types of organisms studied, with vertebrates studied in the field and invertebrates in the lab. We used video monitoring combined with DNA profiling of all of the members of a wild population of field crickets across two generations to capture the factors predicting the reproductive success of males and females. The factors that predict a male's success in gaining mates differ from those that predict how many offspring he has. We confirm the fundamental prediction that males vary more in their reproductive success than females, and we find that females as well as males leave more offspring when they mate with more partners.
Abstract.
Author URL.
Schuett W, Tregenza T, Dall SRX (2010). Sexual selection and animal personality.
Biol Rev Camb Philos Soc,
85(2), 217-246.
Abstract:
Sexual selection and animal personality.
Consistent individual behavioural tendencies, termed "personalities", have been identified in a wide range of animals. Functional explanations for personality have been proposed, but as yet, very little consideration has been given to a possible role for sexual selection in maintaining differences in personality and its stability within individuals. We provide an overview of the available literature on the role of personality traits in intrasexual competition and mate choice in both human and non-human animals and integrate this into a framework for considering how sexual selection can generate and maintain personality. For this, we consider the evolution and maintenance of both main aspects of animal personality: inter-individual variation and intra-individual consistency.
Abstract.
Author URL.
Pincheira-Donoso D, Hodgson DJ, Stipala J, Tregenza T (2009). A phylogenetic analysis of sex-specific evolution of ecological morphology in Liolaemus lizards.
Ecological Research,
24(6), 1223-1231.
Abstract:
A phylogenetic analysis of sex-specific evolution of ecological morphology in Liolaemus lizards
Adaptive radiation theory predicts that phenotypic traits involved in ecological performance evolve in different directions in populations subjected to divergent natural selection, resulting in the evolution of ecological diversity. This idea has largely been supported through comparative studies exploring relationships between ecological preferences and quantitative traits among different species. However, intersexual perspectives are often ignored. Indeed, although it is well established that intersexual competition and sex-specific parental and reproductive roles may often subject sex-linked phenotypes to antagonistic selection effects, most ecomorphological research has explored adaptive evolution on a single sex, or on means obtained from both sexes together. The few studies taking sexual differences into account reveal the occurrence of sex-specific ecomorphs in some clades of lizards, and conclude that the independent contribution of the sexes to the morphological diversity produced by adaptive radiation can be substantial. Here, we investigate whether microhabitat use results in the evolution of sex-specific ecomorphs across 44 Liolaemus lizard species. We found that microhabitat structure does not predict variation in body size and shape in either of the sexes. Yet, we found that males and females tend to occupy significantly different positions in multivariate morphological spaces, indicating that treating males and females as ecologically and phenotypically equivalent units may lead to incomplete or mistaken estimations of the diversity produced by adaptive evolution. © the Ecological Society of Japan 2009.
Abstract.
Davies TE, Beanjara N, Tregenza T (2009). A socio-economic perspective on gear-based management in an artisanal fishery in south-west Madagascar.
Fisheries Management and Ecology,
16(4), 279-289.
Abstract:
A socio-economic perspective on gear-based management in an artisanal fishery in south-west Madagascar
Artisanal fisheries are important socially, nutritionally and economically. Poverty is common in communities dependent on such fisheries, making sustainable management difficult. Poverty based on material style of life (MSL) was assessed, livelihoods surveyed and the relationship between these factors and fishery data collected using a fish landing study were examined. Species richness, diversity, size and mean trophic level of catches were determined for six fishing gears in an artisanal fishery in south-west Madagascar. There was little livelihood diversification and respondents were highly dependent on the fishery. No relationship was found between poverty and gear use. This suggests that poverty does not have a major impact on the nature of the fishery; however, this study was dominated by poor households, so it remains possible that communities with more variation in wealth might show differences in fishing methods according to this parameter. The fishery was heavily exploited with a predominance of small fish in the catches. Beach seines caught some of the smallest fish, overlapped in selectivity with gill nets and also had the highest catch per fishers. Thus, a reduction in the number of beach seines could help reduce the catch of small fish and the overlap in selectivity among gears. © 2009 Blackwell Publishing Ltd.
Abstract.
Gay L, Eady PE, Vasudev R, Hosken DJ, Tregenza T (2009). Costly sexual harassment in a beetle.
Physiological Entomology,
34(1), 86-92.
Abstract:
Costly sexual harassment in a beetle
The optimal number of mating partners for females rarely coincides with that for males, leading to sexual conflict over mating frequency. In the bruchid beetle Callosobruchus maculatus, the fitness consequences to females of engaging in multiple copulations are complex, with studies demonstrating both costs and benefits to multiple mating. However, females kept continuously with males have a lower lifetime egg production compared with females mated only once and then isolated from males. This reduction in fitness may be a result of damage caused by male genitalia, which bear spines that puncture the female's reproductive tract, and/or toxic elements in the ejaculate. However, male harassment rather than costs of matings themselves could also explain the results. In the present study, the fitness costs of male harassment for female C. maculatus are estimated. The natural refractory period of females immediately after their first mating is used to separate the cost of harassment from the cost of mating. Male harassment results in females laying fewer eggs and this results in a tendency to produce fewer offspring. The results are discussed in the context of mate choice and sexual selection. © 2008 the Royal Entomological Society.
Abstract.
Finn JK, Tregenza T, Norman MD (2009). Defensive tool use in a coconut-carrying octopus.
Curr Biol,
19(23), R1069-R1070.
Author URL.
Aarssen LW, Lortie CJ, Budden AE, Koricheva J, Leimu R, Tregenza T (2009). Does publication in top-tier journals affect reviewer behavior?.
PLoS One,
4(7).
Abstract:
Does publication in top-tier journals affect reviewer behavior?
We show that when ecologists act as reviewers their reported rejection rates recommended for manuscripts increases with their publication frequency in high impact factor journals. Rejection rate however does not relate to reviewer age. These results indicate that the likelihood of getting a paper accepted for publication may depend upon factors in addition to scientific merit. Multiple reviewer selection for a given manuscript therefore should consider not only appropriate expertise, but also reviewers that have variable publication experience with a range of different journals to ensure balanced treatment. Interestingly since age did not relate to rejection rates, more senior scientists are not necessarily more jaded in reviewing practices.
Abstract.
Author URL.
Gay L, Eady PE, Vasudev R, Hosken DJ, Tregenza T (2009). Does reproductive isolation evolve faster in larger populations via sexually antagonistic coevolution?.
Biol Lett,
5(5), 693-696.
Abstract:
Does reproductive isolation evolve faster in larger populations via sexually antagonistic coevolution?
Sexual conflict over reproductive investment can lead to sexually antagonistic coevolution and reproductive isolation. It has been suggested that, unlike most models of allopatric speciation, the evolution of reproductive isolation through sexually antagonistic coevolution will occur faster in large populations as these harbour greater levels of standing genetic variation, receive larger numbers of mutations and experience more intense sexual selection. We tested this in bruchid beetle populations (Callosobruchus maculatus) by manipulating population size and standing genetic variability in replicated lines derived from founders that had been released from sexual conflict for 90 generations. We found that after 19 generations of reintroduced sexual conflict, none of our treatments had evolved significant overall reproductive isolation among replicate lines. However, as predicted, measures of reproductive isolation tended to be greater among larger populations. We discuss our methodology, arguing that reproductive isolation is best examined by performing a matrix of allopatric and sympatric crosses whereas measurement of divergence requires crosses with a tester line.
Abstract.
Author URL.
Rodríguez-Muñoz R, Tregenza T (2009). Genetic compatibility and hatching success in the sea lamprey (Petromyzon marinus).
Biol Lett,
5(2), 286-288.
Abstract:
Genetic compatibility and hatching success in the sea lamprey (Petromyzon marinus).
Recent discussion of genetic benefits of polyandry and female mate choice has distinguished between two potential factors influencing offspring quality: (i) some males carry higher quality genes and (ii) males and females differ in their degree of genetic compatibility. We examined evidence for effects of good genes and genetic compatibility on embryonic survival of sea lamprey (Petromyzon marinus), a fish species with external fertilization that spawns in North Atlantic rivers. Using in vitro fertilization, we made all possible crosses among 10 males and 5 females collected in the spawning grounds. Male identity did not have any significant effect on hatching success. However, female identity and male x female interactions had a highly significant effect on hatching success. Our results suggest that genetic compatibility between male and female genomes plays an important role in embryo survival during the early stages of development in the sea lamprey.
Abstract.
Author URL.
Hosken DJ, Stockley P, Tregenza T, Wedell N (2009). Monogamy and the battle of the sexes.
Annu Rev Entomol,
54, 361-378.
Abstract:
Monogamy and the battle of the sexes.
Sexual conflict has been suggested to be important in the evolution of reproductive traits, with much recent theoretical and empirical evidence emphasizing its role in generating sexually antagonistic coevolution in the context of promiscuous mating. Here we shift attention to the role of sexual conflict in a monogamous mating context. Conflicts can arise, for example, when males are successful in imposing monandry at a cost to female fitness, or when females impose monogyny on males. Conflict over remating can also generate monogamy. For example, when males invest heavily in attempting to impose female monandry, the cost of their investment may prevent them from securing additional mates. We emphasize that sexual conflicts need not always generate sexually antagonistic coevolution, and that it is important to consider whether mating decisions are controlled primarily by males or females. Finally, we briefly discuss approaches to distinguish between conflict and classical modes of sexual selection, as this highlights difficulties associated with deciding whether monogamy is enforced by one sex or the other. We suggest that documenting the current fitness consequences of mate choice and mating patterns provides insight into the relative importance of classic and conflict modes of selection.
Abstract.
Author URL.
Brown EA, Gay L, Vasudev R, Tregenza T, Eady PE, Hosken DJ (2009). Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles. Heredity, 103(6), 340-345.
Brown EA, Gay L, Vasudev R, Tregenza T, Eady PE, Hosken DJ (2009). Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles.
Heredity (Edinb),
103(4), 340-345.
Abstract:
Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles.
Reproduction can be costly and is predicted to trade-off against other characters. However, while these trade-offs are well documented for females, there has been less focus on aspects of male reproduction. Furthermore, those studies that have looked at males typically only investigate phenotypic associations, with the underlying genetics often ignored. Here, we report on phenotypic and genetic trade-offs in male reproductive effort in the seed beetle, Callosobruchus maculatus. We find that the duration of a male's first copulation is negatively associated with subsequent male survival, phenotypically and genetically. Our results are consistent with life-history theory and suggest that like females, males trade-off reproductive effort against longevity.
Abstract.
Author URL.
Finn J, Tregenza T, Norman M (2009). Preparing the perfect cuttlefish meal: complex prey handling by dolphins.
PLoS One,
4(1).
Abstract:
Preparing the perfect cuttlefish meal: complex prey handling by dolphins.
Dolphins are well known for their complex social and foraging behaviours. Direct underwater observations of wild dolphin feeding behaviour however are rare. At mass spawning aggregations of giant cuttlefish (Sepia apama) in the Upper Spencer Gulf in South Australia, a wild female Indo-Pacific bottlenose dolphin (Tursiops aduncus) was observed and recorded repeatedly catching, killing and preparing cuttlefish for consumption using a specific and ordered sequence of behaviours. Cuttlefish were herded to a sand substrate, pinned to the seafloor, killed by downward thrust, raised mid-water and beaten by the dolphin with its snout until the ink was released and drained. The deceased cuttlefish was then returned to the seafloor, inverted and forced along the sand substrate in order to strip the thin dorsal layer of skin off the mantle, thus releasing the buoyant calcareous cuttlebone. This stepped behavioural sequence significantly improves prey quality through 1) removal of the ink (with constituent melanin and tyrosine), and 2) the calcareous cuttlebone. Observations of foraging dolphin pods from above-water at this site (including the surfacing of intact clean cuttlebones) suggest that some or all of this prey handling sequence may be used widely by dolphins in the region. Aspects of the unique mass spawning aggregations of giant cuttlefish in this region of South Australia may have contributed to the evolution of this behaviour through both high abundances of spawning and weakened post-spawning cuttlefish in a small area (>10,000 animals on several kilometres of narrow rocky reef), as well as potential long-term and regular visitation by dolphin pods to this site.
Abstract.
Author URL.
Bretman A, Newcombe D, Tregenza T (2009). Promiscuous females avoid inbreeding by controlling sperm storage.
Mol Ecol,
18(16), 3340-3345.
Abstract:
Promiscuous females avoid inbreeding by controlling sperm storage.
Recent studies in a variety of species have shown that polyandrous females are somehow able to bias paternity against their relatives postcopulation, although how they do so remains unknown. Field crickets readily mate with their siblings, but when also mated to an unrelated male, they produce disproportionately fewer inbred offspring. We use a new competitive microsatellite polymerase chain reaction technique to determine the contribution of males to stored sperm and subsequent paternity of offspring. Paternity is almost completely predicted by how much sperm from a particular male is stored, and unrelated males contribute more sperm to storage and have a corresponding higher paternity success.
Abstract.
Author URL.
Tregenza T, Attia F, Bushaiba SS (2009). Repeatability and heritability of sperm competition outcomes in males and females of Tribolium castaneum.
Behavioral Ecology and Sociobiology,
63(6), 817-823.
Abstract:
Repeatability and heritability of sperm competition outcomes in males and females of Tribolium castaneum
Differences among males in their success in achieving fertilisations when females mate with more than one partner are now recognised as an important target of sexual selection. However, very few studies have attempted to determine whether particular males are consistently successful in sperm competition and whether success in sperm competition is a heritable trait. Additionally, the potential heritability of female traits that influence the outcome of sperm competition has received only limited attention. Using the polyandrous beetle Tribolium castaneum, we examined repeatability of male success in sperm competition by mating pairs of males carrying different visible genetic markers to a string of different females. Males showed consistency in their ability to successfully transfer sperm to females, but not in their success in sperm competition. Furthermore, when we independently compared success in sperm competition of fathers with their sons, we found no evidence for heritability of this trait. Similarly, females that exhibited high or low first male sperm precedence did not tend to have daughters that showed the same pattern. Our results suggest that we should be wary of assuming that success in sperm competition is heritable through either sex. © 2009 Springer-Verlag.
Abstract.
Gay L, Hosken DJ, Vasudev R, Tregenza T, Eady PE (2009). Sperm competition and maternal effects differentially influence testis and sperm size in Callosobruchus maculatus.
J Evol Biol,
22(5), 1143-1150.
Abstract:
Sperm competition and maternal effects differentially influence testis and sperm size in Callosobruchus maculatus.
The evolutionary factors affecting testis size are well documented, with sperm competition being of major importance. However, the factors affecting sperm length are not well understood; there are no clear theoretical predictions and the empirical evidence is inconsistent. Recently, maternal effects have been implicated in sperm length variation, a finding that may offer insights into its evolution. We investigated potential proximate and microevolutionary factors influencing testis and sperm size in the bruchid beetle Callosobruchus maculatus using a combined approach of an artificial evolution experiment over 90 generations and an environmental effects study. We found that while polyandry seems to select for larger testes, it had no detectable effect on sperm length. Furthermore, population density, a proximate indicator of sperm competition risk, was not significantly associated with sperm length or testis size variation. However, there were strong maternal effects influencing sperm length.
Abstract.
Author URL.
Green K, Tregenza T (2009). The influence of male ejaculates on female mate search behaviour, oviposition and longevity in crickets.
Animal Behaviour,
77(4), 887-892.
Abstract:
The influence of male ejaculates on female mate search behaviour, oviposition and longevity in crickets
In animals with internal fertilization, sperm are transferred in ejaculates, which include water and proteins produced by male accessory glands. These proteins help to protect and facilitate sperm passage, and in some species have been identified as having an influence on female behaviour and life history traits. They may increase oviposition rate, reduce sexual receptivity and decrease female life span. Virgin female field crickets Gryllus bimaculatus orient and move towards calling song produced by males. However, phonotaxis is greatly reduced after mating. We tested the hypothesis that female phonotaxis, oviposition and longevity are influenced by compounds in male ejaculates. We divided females into two groups: one injected with seminal proteins extracted from spermatophores from which sperm had been removed, and one injected with Ringer's solution. We measured female egg laying and phonotaxis before and after treatment, and recorded female longevity. We did not detect an effect of treatment on either egg laying or phonotaxis. However, females treated with seminal proteins moved less overall and died sooner than females in the control group. We therefore failed to find any evidence that postmating reductions in phonotaxis are due to effects of male seminal proteins. However, the reduction in female movement after treatment with seminal proteins could reduce their likelihood of subsequent matings. © 2009 the Association for the Study of Animal Behaviour.
Abstract.
Borsuk RM, Aarssen LW, Budden AE, Koricheva J, Leimu R, Tregenza T, Lortie CJ (2009). To name or not to name: the effect of changing author gender on peer review.
BioScience,
59(11), 985-989.
Abstract:
To name or not to name: the effect of changing author gender on peer review
The peer review model is one of the most important tools used in science to assess the relative merit of research. We manipulated a published article to reflect one of the following four author designations: female, male, initial, and no name provided. This article was then reviewed by referees of both genders at various stages of scientific training. Name changing did not influence acceptance rates or quality ratings. Undergraduate referees were less critical than graduate students or postdoctoral researchers, independent of gender. However, female postdoctoral researchers were the most critical referees: Their rejection rates were the highest and quality ratings the lowest, regardless of the author name provided. Contrary to previous reports in the literature, there was no evidence of same-gender preferences. This study strongly suggests that female postgraduate biologists may apply different expectations to peer review. © 2009 by American Institute of Biological Sciences. All rights reserved.
Abstract.
Edvardsson M, Rodríguez-Muñoz, R. Tregenza, T. (2008). 2008 No evidence that female Callosobruchus maculatus use remating to reduce costs of inbreeding. Animal Behaviour, 75, 1519-1524.
Rodríguez-Muñoz R, Ojanguren AF, Tregenza T (2008). Comment on "International conservation policy delivers benefits for birds in Europe".
Science,
319(5866).
Abstract:
Comment on "International conservation policy delivers benefits for birds in Europe".
Donald et al. (Reports, 10 August 2007, p. 810) assessed the impact of the European Union's Birds Directive, a conservation policy enacted in 1979, and reported evidence for positive population changes in targeted species. We argue that their conclusions are overstatements based on unsuitable data and inappropriate analyses.
Abstract.
Author URL.
Pincheira-Donoso D, Hodgson DJ, Tregenza T (2008). Comparative evidence for strong phylogenetic inertia in precloacal signalling glands in a species-rich lizard clade. Evolutionary Ecology Research, 10, 11-28.
Budden AE, Aarssen LW, Koricheva J, Leimu R, Lortie CJ, Tregenza T (2008). Does double-blind review favor female authors? Reply.
FRONTIERS IN ECOLOGY AND THE ENVIRONMENT,
6(7), 356-357.
Author URL.
Leimu R, Lortie CJ, Aarssen L, Budden AE, Koricheva J, Tregenza T (2008). Does it pay to have a "bigwig" as a co-author?. Frontiers in Ecology and the Environment, 6(8), 410-411.
Budden AE, Tregenza T, Aarssen W, Koricheva JK, Leimu R, Lortie CJ (2008). Double-blind review favours increased representation of female authors. Trends in Ecology & Evolution, 23, 4-6.
Budden, A.E. Tregenza, T, Aarssen, W. Koricheva, J.K. Leimu, R. Lortie, C. J. (2008). Double-blind review: Accept with minor revisions. Trends in Ecology & Evolution, 23, 353-354.
Leimu R, Lortie CJ, Tregenza T, Koricheva J, Budden AE, Aarssen L (2008). How big are bigwigs?: a reply to Havens. Frontiers in Ecology and the Environment, 6(10).
Wright, L, Tregenza, T. Hosken, D.J. (2008). Inbreeding, inbreeding depression and extinction. Conservation Genetics, 9, 833-843.
Smallegange IM, Tregenza T (2008). Local Competition Between Foraging Relatives: Growth and Survival of Bruchid Beetle Larvae.
J Insect Behav,
21(5), 375-386.
Abstract:
Local Competition Between Foraging Relatives: Growth and Survival of Bruchid Beetle Larvae.
Kin selection theory states that when resources are limited and all else is equal, individuals will direct competition away from kin. However, when competition between relatives is completely local, as is the case in granivorous insects whose larval stages spend their lives within a single seed, this can reduce or even negate the kin-selected benefits. Instead, an increase in competition may have the same detrimental effects on individuals that forage with kin as those that forage with non-kin. In a factorial experiment we assessed the effects of relatedness and competition over food on the survival and on fitness-related traits of the bruchid beetle Callosobruchus maculatus. Relatedness of competitors did not affect the survival of larvae. Larval survival substantially decreased with increasing larval density, and we found evidence that beetles maturing at a larger size were more adversely affected by competition, resulting in lower survival rates. Furthermore, females showed a reduction in their growth rate with increasing larval density, emerging smaller after the same development time. Males increased their growth rate, emerging earlier but at a similar size when food was more limited. Our results add to the growing number of studies that fail to show a relationship between relatedness and a reduction in competition between relatives in closed systems, and emphasize the importance of the scale at which competition between relatives occurs.
Abstract.
Author URL.
Bretman, A, Dawson, D.A. Horsburgh, G.J. Tregenza, T. (2008). New microsatellite loci isolated from the field cricket <em>Gryllus bimaculatus</em> characterized in two cricket species, <em>Gryllus bimaculatus</em> and <em>Gryllus campestris</em>. Molecular Ecology Resources, 3, 191-195.
Edvardsson M, Rodríguez-Muñoz R, Tregenza T (2008). No evidence that female bruchid beetles, Callosobruchus maculatus, use remating to reduce costs of inbreeding.
Animal Behaviour,
75(4), 1519-1524.
Abstract:
No evidence that female bruchid beetles, Callosobruchus maculatus, use remating to reduce costs of inbreeding
Despite the often dramatic negative effects of inbreeding on offspring fitness, matings between closely related individuals sometimes occur. This may be because females cannot reliably recognize related males before mating with them. As an alternative to precopulatory choice, polyandrous females may avoid inbreeding through postcopulatory mechanisms if they can assess mate relatedness during or after copulation. These mechanisms include increasing remating propensity and decreasing rate of offspring production in response to incestuous matings. Stored product pests, such as the bruchid beetle Callosobruchus maculatus, have an ecology that is likely to expose them to frequent risks of inbreeding when a small number of females found a new population on a previously uninfested store of beans. Using this species, we show that inbreeding has negative effects on offspring viability but that females do not appear to discriminate between brothers and unrelated males prior to mating. Furthermore, females that first mated with brothers did not increase their remating propensity or decrease their rate of offspring production relative to females that first mated with unrelated males. Our findings suggest that the costs of inbreeding have not been sufficient to drive the evolution of mating behaviour as a mechanism of inbreeding avoidance in C. maculatus. © 2007 the Association for the Study of Animal Behaviour.
Abstract.
Tregenza, T. Simmons, L.W. (2008). Nuptial gifts fail to resolve a sexual conflict in an insect. BMC Evolutionary Biology, 8
Budden AE, Lortie CJ, Tregenza T, Aarssen L, Koricheva J, Leimu R (2008). Response to Webb et al.: Double-blind review: accept with minor revisions. Trends in Ecology and Evolution, 23(7), 353-354.
Budden AE, Aarssen L, Koricheva J, Leimu R, Lortie CJ, Tregenza T (2008). Response to Whittaker: challenges in testing for gender bias. Trends in Ecology and Evolution, 23(9), 480-481.
Rodríguez-Muñoz R, Bretman A, Hadfield JD, Tregenza T (2008). Sexual selection in the cricket <em>Gryllus bimaculatus</em>: No good genes?. Genetica, 132, 287-294.
Rodríguez-Muñoz R, Bretman A, Hadfield JD, Tregenza T (2008). Sexual selection in the cricket Gryllus bimaculatus: no good genes?.
Genetica,
134(1), 129-136.
Abstract:
Sexual selection in the cricket Gryllus bimaculatus: no good genes?
Recent studies have suggested that females of the field cricket Gryllus bimaculatus exercise post-copulatory choice over the paternity of their offspring. There is evidence that these choices are made in relation to the genetic compatibility of mates rather than their absolute quality, but the magnitude of heritable differences in males has not been thoroughly examined. Using a half-sib breeding design we measured additive genetic variance and dam effects in a suite of reproductive and non-reproductive traits. Both components explained relatively little of the phenotypic variance across traits. The dam component in our design contains variance caused by both maternal effects and dominance. If maternal effects are negligible as suggested by previous studies, our data suggest that dominance variance is an important source of variation in these traits. The lack of additive genetic variation, but possible existence of large amounts of non-additive genetic variation is consistent with the idea that female mate choice and multiple mating may be driven by differences in genetic compatibility between potential mates rather than by differences in genetic quality.
Abstract.
Author URL.
Grod ON, Budden AE, Tregenza T, Koricheva J, Leimu R, Aarssen LW, Lortie CJ (2008). Systematic variation in reviewer practice according to country and gender in the field of ecology and evolution.
PLoS One,
3(9).
Abstract:
Systematic variation in reviewer practice according to country and gender in the field of ecology and evolution.
The characteristics of referees and the potential subsequent effects on the peer-review process are an important consideration for science since the integrity of the system depends on the appropriate evaluation of merit. In 2006, we conducted an online survey of 1334 ecologists and evolutionary biologists pertaining to the review process. Respondents were from Europe, North America and other regions of the world, with the majority from English first language countries. Women comprised a third of all respondents, consistent with their representation in the scientific academic community. Among respondents we found no correlation between the time typically taken over a review and the reported average rejection rate. On average, Europeans took longer over reviewing a manuscript than North Americans, and females took longer than males, but reviewed fewer manuscripts. Males recommended rejection of manuscripts more frequently than females, regardless of region. Hence, editors and potential authors should consider alternative sets of criteria, to what exists now, when selecting a panel of referees to potentially balance different tendencies by gender or region.
Abstract.
Author URL.
Budden AE, Aarssen LW, Koricheva J, Leimu R, Lortie CJ, Tregenza T (2008). The authors respond. Frontiers in Ecology and the Environment, 6(7), 354-355.
Pincheira-Donoso D, Hodgson DJ. Tregenza T (2008). The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards?. BMC Evolutionary Biology, 8
Cornell S, Tregenza T (2007). A new theory for the evolution of polyandry as a means of inbreeding avoidance. Proceedings of the Royal Society B, 274, 2873-2879.
Tregenza, T. Hodgson, D.J. (2007). Body size evolution in South American Liolaemus lizards of the boulengeri clade: a contrasting reassessment. Journal of Evolutionary Biology, 20, 2067-2071.
Rodríguez-Muñoz R, Mirol PM, Segelbacher G, Ferná, ndez A, Tregenza T (2007). Genetic differentiation of an endangered capaercallie (<em>Tetrao urogallus</em>) population at the Southern edge of the species range. Conservation Genetics, 8, 659-670.
Edvardsson M, Champion de Crespigny FE, Tregenza T (2007). Mating behaviour: promiscuous mothers have healthier young.
Curr Biol,
17(2), R66-R67.
Abstract:
Mating behaviour: promiscuous mothers have healthier young.
A small marsupial has thrown new light on the question of why females typically mate with several males: promiscuous female antechinuses have many more surviving offspring because males that are successful in sperm competition also sire healthy offspring.
Abstract.
Author URL.
Lortie CJ, Aarssen LW, Budden AE, Korichva JK, Leimu R, Tregenza T (2007). Publication bias and merit in ecology. Oikos, 116, 1247-1253.
Lortie CJ, Aarssen LW, Budden AE, Koricheva JK, Leimu R, Tregenza T (2007). Publication bias and merit in ecology.
Oikos,
116(7), 1247-1253.
Abstract:
Publication bias and merit in ecology
Bias, or any set of factors that influence the general expression of merit, is common in science and is an inevitable by‐product of an imperfect but otherwise reasonably objective human pursuit to understand the world we inhabit. In this paper, we explore the conceptual significance of a relatively tractable form of bias, namely publication and dissemination bias. A specific definition is developed, a working model of classification for publication bias is proposed, and an assessment of what we can measure is described. Finally, we offer expectations for ecologists with respect to the significance of bias in the publication process within our discipline. We argue that without explicit consideration of both the qualitative and quantitative aspects of publication bias in ecology, we limit our capacity to fairly assess and best use the science that we as a community produce.
Abstract.
Bretman A, Tregenza T (2007). Strong, silent types: the rapid, adaptive disappearance of a sexual signal.
Trends Ecol Evol,
22(5), 226-228.
Abstract:
Strong, silent types: the rapid, adaptive disappearance of a sexual signal.
To see evolution in action, it helps to be in the right place at the right time. In a recent study, Zuk et al. document the rapid evolution of a sexual signal in crickets on a Hawaiian island and suggest that it is a response to parasitism. A new male morph has appeared that cannot sing, and so does not attract an acoustically orientating parasite. The disadvantage of this, however, is that silent males might not be able to attract mates. The authors suggest that plasticity in male aggregating behaviour can provide an escape from the costs of this potentially maladaptive trait.
Abstract.
Author URL.
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies.
SCIENCE,
312(5774), 689-690.
Author URL.
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies [2]. Science, 312(5774), 689-690.
Shuker DM, Tregenza T (2006). Debating sexual selection and mating strategies [9]. Science, 312(5774), 693-694.
Shuker DM, Tregenza T (2006). Debating sexual selection and mating strategies.
Science,
312(5774), 689-697.
Author URL.
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies.
Science,
312(5774), 689-697.
Author URL.
Hosken, DJ, Tregenza, T. (2006). Evolution; Inbreeding, Multiple mating and Embryonic Aid. Current Biology, 16(6), R202-R203.
Tregenza, T. Simmons, L.W. Wedell, N. & Zuk, M. (2006). Female preference for male courtship song and its role as a signal of immune function and condition. Animal Behaviour, 72, 809-118.
Tregenza T, Wedell N, Chapman T (2006). Introduction. Sexual conflict: a new paradigm?.
Philos Trans R Soc Lond B Biol Sci,
361(1466), 229-234.
Author URL.
Rodríguez-Muñoz, R. Tregenza, T. (2006). Male dominance determines female egg laying rate in crickets. Biology Letters, 2, 409-411.
Wedell, N. Beveridge, M. Tregenza, T. (2006). Post-copulatory inbreeding avoidance by female crickets only revealed by molecular markers. Molecular Ecology, 15(12), 3817-3824.
Shuker D & Tregenza T (2006). Reply to Roughgarden - Sexual selection happens. Science, 312, 693-694.
Wedell, N. Chapman, T.C. (2006). Sexual conflict - a new paradigm?. Philosophical Transactions of the Royal Society, 361, 229-234.
Kvarnemo, L. Lessells, C.M. Tregenza (2006). Sexual conflict and life histories. Animal Behaviour, 71, 999-1011.
Hosken DJ, Tregenza T (2005). Evolution: do bad husbands make good fathers?.
Curr Biol,
15(20), R836-R838.
Abstract:
Evolution: do bad husbands make good fathers?
Males sometimes harm their mates as they seek to maximise the number of offspring they sire. But are females really suffering or do the benefits of having sons that inherit their father's manipulative traits make up for the costs? Three recent studies provide the first hard data addressing this issue, but they differ in their conclusions.
Abstract.
Author URL.
Hosken, D.J. Tregenza, T (2005). Mate choice; Been there, done that. Current Biology, 15(23), R959-R961.
Tregenza T, Bretman AJ (2005). Measuring polyandry in wild populations: a case study using promiscuous crickets. Molecular Ecology, 14(7), 2169-2179.
Tregenza, T. Hosken DJ (2005). Sexual selection: Do bad husbands make good fathers?. Current Biology, 15(20), R836-R838.
Butlin RK, Tregenza T (2005). The way the world might be.
J Evol Biol,
18(5), 1205-1208.
Author URL.
Tregenza, T. (2005). Why do male <em>Callosobruchus maculatus</em> harm their mates?. Behavioral Ecology, 16, 788-793.
Tregenza, T. (2004). Divergence revealed by population crosses in the red flour beetle <em>Tribolium castaneum</em>. Evolutionary Ecology Research, 6, 927-935.
Radwan, J. Kotiaho, J.S. (2004). Genic capture and resolving the lek paradox. Trends in Ecology & Evolution, 19, 323-328.
Bretman AJ, Wedell N, Tregenza T (2004). Molecular evidence of post-copulatory inbreeding avoidance in the field cricket Gryllus bimaculatus. Proceedings of the Royal Society B Biological Sciences, 271(1535), 159-164.
Wedell, N. (2004). Proceedings of the Royal Society B 271, 'Molecular evidence of post-copulatory inbreeding avoidance in the field cricket <em>Gryllus bimaculatus</em>'. , 159-164.
Tregenza T (2003). Evolution: the battle between the sexes.
Nature,
423(6943), 929-930.
Author URL.
Tregenza T, Hosken DJ, Ward PI, Wedell N (2003). Maternal effects on offspring depend on female mating pattern and offspring environment in yellow dung flies. Evolution, 57(2), 297-304.
Bretman, A.J. Tregenza, T. (2003). Microsatellite loci for the field cricket, <em>Gryllus bimaculatus</em> and their cross-utility in other species of Orthoptera. Molecular Ecology Notes, 3, 191-195.
Hosken DJ, Garner, T.W.J. Tregenza, T. Wedell N, Ward PI (2003). Superior sperm competitors sire higher quality young. Proceedings of the Royal Society of London B, 270, 1933-1938.
Tregenza, T. (2003). The battle between the sexes. Nature, 423, 929-930.
Tregenza, T. Butlin, R.K. (2003). Transitions in cuticular composition across a hybrid zone – historical accident or environmental adaptation?. Biological Journal of the Linnean Society, 78, 193-201.
Tregenza, T. (2002). Divergence and reproductive isolation in the early stages of speciation. Genetica, 116, 291-300.
Finn, J. Paul, D. (2002). Extreme sexual size dimorphism. New Zealand Journal of Freshwater and Marine Biology, 36, 733-736.
Norman MD, Paul D, Finn J, Tregenza T (2002). First encounter with a live male blanket octopus: the world's most sexually size-dimorphic large animal.
New Zealand Journal of Marine and Freshwater Research,
36(4), 733-736.
Abstract:
First encounter with a live male blanket octopus: the world's most sexually size-dimorphic large animal
The first encounter with a live male blanket octopus, Tremoctopus violaceus Chiaie, 1830, illustrates the most extreme example of sexual size-dimorphism in a non-microscopic animal. Females attain sizes of up to 2 m long—almost 2 orders of magnitude larger than the 2.4-cm-long male. Weight ratios between the sexes are at least 10 000:1 and are likely to reach 40 000:1. Sexual selection and the unique defensive strategy of carrying cnidarian stinging tentacles may both have contributed to the evolution of this extreme size-dimorphism. Such dimorphism is not seen in any other animal remotely as large. © 2002, Copyright Taylor & Francis Group, LLC.
Abstract.
Tregenza, T. (2002). Gender bias in the refereeing process?. Trends in Ecology & Evolution, 349-350.
Ward PI, Wedell, N. Hosken, D.J. Tregenza T (2002). Measuring the sperm competition successes of field males of the yellow dung fly. Ecological Entomology, 27, 763-765.
Tregenza, T. Wedell, N. (2002). Oviposition preference and geographic specialization by the mrymecophilous butterfly <em>Jalmenus evagoras</em> (Lepidoptera: Lycaenidae) in response to attendant ants. Journal of Evolutionary Biology, 15, 861-870.
Fraser AM, Tregenza T, Wedell N, Elgar MA, Pierce NE (2002). Oviposition tests of ant preference in a myrmecophilous butterfly.
Journal of Evolutionary Biology,
15(5), 861-870.
Abstract:
Oviposition tests of ant preference in a myrmecophilous butterfly
Butterflies in the family Lycaenidae that have obligate associations with ants frequently exhibit ant-dependent egg laying behaviour. In a series of field and laboratory choice tests, we assessed oviposition preference of the Australian lycaenid Jalmenus evagoras in response to different species and populations of ants. Females discriminated between attendant and nonattendant ant species, between attendant ant species, and to some extent, between populations of a single ant species. When preferences were found, ovipositing butterflies preferred their locally predominant attendant ant species and geographically proximate attendant ant populations. A reciprocal choice test using adults from a generation of butterflies reared in the absence of ants indicated a genetic component to oviposition preference. Individual females were flexible with respect to oviposition site choice, often ovipositing on more than one treatment during a trial. Preferences arose from a hierarchical ranking of ant treatments. These results are discussed in terms of local adaptation and its possible significance in the diversification of ant-associated lycaenids.
Abstract.
Tregenza T, Wedell N (2002). Polyandrous females avoid costs of inbreeding. Nature, 415(6867), 71-73.
Pritchard, V.L. Butlin, R.K. (2002). The origins of postmating reproductive isolation: testing hypotheses in the grasshopper <em>Chorthippus parallelus</em>. Population Ecology, 44, 137-144.
Finn, J. Tregenza, T. (2001). Dynamic mimicry in an Indo-Malayan octopus. Proceedings of the Royal Society B, 268, 1755-1758.
Butlin, R.K. Zuk, M. (2001). Sexual selection and speciation. Trends in Ecology & Evolution, 16, 364-371.
Liimatainen, J.O. Tregenza, T. Hoikkala, A. (2000). Courtship signals and mate choice of the flies of inbred <em>Drosophila montana</em> strains. Journal of Evolutionary Biology, 13, 583-592.
Payne RJH, Krakauer DC (2000). Disruptive sexual selection.
TRENDS IN ECOLOGY & EVOLUTION,
15(10), 419-420.
Author URL.
Bridle JR, Jiggins CD, Tregenza T (2000). Disruptive sexual selection - Reply.
TRENDS IN ECOLOGY & EVOLUTION,
15(10), 420-420.
Author URL.
Payne RJH, Krakauer DC, Bridle JR, Jiggins CD, Tregenza T (2000). Disruptive sexual selection [3] (multiple letters). Trends in Ecology and Evolution, 15(10), 419-420.
Butlin RK, Tregenza T (2000). Erratum: Levels of genetic polymorphism: Marker loci versus quantitative traits (Phil. Trans. R. Soc. Lond. B (February 1998) 353 (187-198)). Philosophical Transactions of the Royal Society B: Biological Sciences, 355(1404).
Tregenza, T. (2000). Evolutionarily dynamic sperm. Trends in Ecology & Evolution, 15, 85-86.
Tregenza T, Butlin RK, Wedell N (2000). Evolutionary biology: Sexual conflict and speciation. Nature, 407(6801), 149-150.
Tregenza T, Wedell N (2000). Genetic compatibility, mate choice and patterns of parentage: invited review.
Mol Ecol,
9(8), 1013-1027.
Abstract:
Genetic compatibility, mate choice and patterns of parentage: invited review.
There is growing interest in the possibility that genetic compatibility may drive mate choice, including gamete choice, particularly from the perspective of understanding why females frequently mate with more than one male. Mate choice for compatibility differs from other forms of choice for genetic benefits (such as 'good genes') because individuals are expected to differ in their mate preferences, changing the evolutionary dynamics of sexual selection. Recent experiments designed to investigate genetic benefits of polyandry suggest that mate choice on the basis of genetic compatibility may be widespread. However, in most systems the mechanisms responsible for variation in compatibility are unknown. We review potential sources of variation in genetic compatibility and whether there is any evidence for mate choice driven by these factors. Selfish genetic elements appear to have the potential to drive mate compatibility mate choice, though as yet there is only one convincing example. There is abundant evidence for assortative mating between populations in hybrid zones, but very few examples where this is clearly a result of selection against mating with genetically less compatible individuals. There are also numerous cases of inbreeding avoidance, but little evidence that mate choice or differential fertilization success driven by genetic compatibility occurs between unrelated individuals. The exceptions to this are a handful of situations where both the alleles causing incompatibility and the alleles involved in mate choice are located in a chromosome region where recombination is suppressed. As yet there are only a few potential sources of genetic compatibility which have clearly been shown to drive mate choice. This may reflect limitations in the potential for the evolution of mate choice for genetic compatibility within populations, although the most promising sources of such incompatibilities have received relatively little research.
Abstract.
Author URL.
Buckley, S.H. Pritchard, V.L. Butlin, R.K. (2000). Inter- and intrapopulation effects of sex and age on epicuticular composition of meadow grasshopper, <em>Chorthippus parallelus</em>. Journal of Chemical Ecology, 26, 257-278.
Butlin RK, Tregenza T (2000). Levels of genetic polymorphism: marker loci versus quantitative traits (vol B353, pg 187, 1998).
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES,
355(1404), 1865-1865.
Author URL.
Tregenza T, Pritchard VL, Butlin RK (2000). Patterns of trait divergence between populations of the meadow grasshopper, Chorthippus parallelus.
Evolution,
54(2), 574-585.
Abstract:
Patterns of trait divergence between populations of the meadow grasshopper, Chorthippus parallelus.
To understand the process of speciation, we need to identify the evolutionary phenomena associated with divergence between populations of the same species. A powerful approach is to compare patterns of trait differences between populations differing in their evolutionary histories. A recent study of genetic divergence between populations of the meadow grasshopper Chorthippus parallelus, from different locations around Europe has allowed us to use this species to investigate which aspects of evolutionary history are associated with divergence in morphology and mating signals. During the last glaciation C. parallelus was confined to a number of refugia in southern Europe and has subsequently recolonized the northern part of the continent. This process of isolation followed by range expansion has created populations differing markedly in their evolutionary pasts--some have been isolated from one another for thousands of years, others have undergone repeated founder events, and others now live in sympatry with a closely related species. Using laboratory-reared grasshoppers from 12 different populations with a range of evolutionary histories, we quantify differences in morphology, chemical signals, and male calling-song. The observed pattern of divergence between these populations is then compared with the pattern predicted by hypotheses about what drives divergence. This comparison reveals that long periods in allopatry and processes associated with repeated founder events are both strongly associated with divergence.
Abstract.
Author URL.
Jiggins, C. Tregenza, T. (2000). Reply to Payne and Krakauer. Trends in Ecology & Evolution, 15
Tregenza T, Butlin RK, Wedell N (2000). Sexual conflict and speciation.
Nature,
407(6801), 149-150.
Author URL.
Wedell, N. Butlin, R.K. (2000). Speciation and sexual conflict. Nature, 407, 149-150.
Pritchard, V.L. Butlin, R.K. (2000). The origins of premating reproductive isolation: testing hypotheses in the grasshopper <em>Chorthippus parallelus</em>. Evolution, 54, 1687-1698.
Finn, J. Tregenza, T. (1999). Female impersonation as an alternative reproductive strategy in giant cuttlefish. Proceedings of the Royal Society B, 266, 1347-1349.
Tregenza T, Butlin RK (1999). Erratum: Speciation without isolation (Nature (1999) 400 (311-312)). Nature, 400(6744).
Wedell N, Tregenza T (1999). SUCCESSFUL FATHERS SIRE SUCCESSFUL SONS.
Evolution,
53(2), 620-625.
Abstract:
SUCCESSFUL FATHERS SIRE SUCCESSFUL SONS.
The theory of sexual selection holds a central role in evolutionary biology. Its key assumption is the heritability of traits associated with reproductive success. Strong indirect evidence supporting this assumption comes from the numerous studies that have identified heritable traits associated with mating success. However, there remain only a handful of studies that have attempted to demonstrate directly that successful fathers have successful sons. We present the results of an experimental study of the mating success and phenotype of male field crickets Gryllus bimaculatus (Orthoptera: Gryllidae) and their offspring. These reveal that sons of successful males obtain significantly more copulations than sons of unsuccessful males. There was no difference in body size of sons of either group, but sons of successful males had significantly longer development times. This may represent a naturally selected cost to traits associated with success that could balance their sexually selected advantages.
Abstract.
Author URL.
Butlin, R.K. (1999). Speciation without isolation. Nature, 400, 311-312.
Tregenza T, Butlin RK (1999). Speciation without isolation (vol 400, pg 311, 1999).
NATURE,
400(6744), 513-513.
Author URL.
Tregenza, T. (1999). Successful fathers sire successful sons. Evolution, 53, 620-625.
Tregenza T, Wedell N (1998). BENEFITS OF MULTIPLE MATES IN THE CRICKET GRYLLUS BIMACULATUS.
Evolution,
52(6), 1726-1730.
Abstract:
BENEFITS OF MULTIPLE MATES IN THE CRICKET GRYLLUS BIMACULATUS.
Despite the importance of polyandry for sexual selection, the reasons why females frequently mate with several males remain poorly understood. A number of genetic benefits have been proposed, based on the idea that by taking multiple mates, females increase the likelihood that their offspring will be sired by genetically more compatible or superior males. If certain males have intrinsically "good genes," any female mating with them will produce superior offspring. Alternatively, if some males have genetic elements that are incompatible with a particular female, then she may benefit from polyandry if the sperm of such males are less likely to fertilize her eggs. We examined these hypotheses in the field cricket Gryllus bimaculatus (Orthoptera: Gryllidae). By allocating females identical numbers of matings but different numbers of mates we investigated the influence of number of mates on female fecundity, and both short- and long-term offspring fitness. This revealed no effect of number of mates on number of eggs laid. However, hatching success of eggs increased with number of mates. This effect could not be attributed to nongenetic effects such as the possibility that polyandry reduces variance in the quantity or fertilizing ability of sperm females receive, because a control group receiving half the number of copulations showed no drop in hatching success. Offspring did not differ in survival, adult mass, size, or development time with treatment. When males were mated to several different females there were no repeatable differences between individual males in the hatching success of their mate's eggs. This suggests that improved hatching success of polyandrous females is not due to certain males having genes that improve egg viability regardless of their mate. Instead, our results support the hypothesis that certain males are genetically more compatible with certain females, and that this drives polyandry through differential fertilization success of sperm from more compatible males.
Abstract.
Author URL.
Wedell, N. (1998). Benefits of multiple mates in the cricket <em>Gryllus bimaculatus</em>. Evolution, 52, 1726-1730.
Tregenza, T. (1998). Levels of genetic polymorphism: marker loci versus quantitative traits. Philosophical Transactions of the Royal Society, 353, 187-198.
Parker GA, Partridge L (1998). Sexual conflict and speciation.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES,
353(1366), 261-274.
Author URL.
Thompson, D.J. (1998). Unequal competitor ideal free distribution in fish?. Evolution and Ecology, 12, 655-666.
Tregenza, T. (1997). Alphabetical orders. Nature, 388
Tregenza, T. (1997). Darwin a better name than Wallace?. Nature, 385
Wedell, N. (1997). Definitive evidence for cuticular pheromones in a cricket. Animal Behaviour, 54, 979-984.
Butlin RK, Tregenza T (1997). Evolutionary biology - is speciation no accident?.
NATURE,
387(6633), 551-&.
Author URL.
Tregenza, T. (1997). Is speciation no accident?. Nature, 387, 551-552.
Wedell, N. (1997). Natural selection bias?. Nature, 386
Tregenza, T. Butlin, R.K. (1997). Speciation and signal trait genetics. Trends in Ecology & Evolution, 12, 299-301.
Bridle, J.R. (1997). The diversity of speciation. Trends in Ecology & Evolution, 12, 382-383.
Tregenza T (1997). What's up, doc?. New Scientist, 155(2099).
Shaw, J.J. Thompson, D.J. (1996). An experimental investigation of a new ideal free distribution model. Evolution and Ecology, 10, 45-49.
Parker, G.A. Thompson, D.J. (1996). Interference and the ideal free distribution: Models and tests. Behavioral Ecology, 7, 379-386.
Thompson, D.J. Parker, G.A. (1996). Interference and the ideal free distribution: Oviposition in a parasitoid wasp. Behavioral Ecology, 7, 387-394.
Tregenza T, Hack MA, Thompson DJ (1996). Relative competitive success of unequal competitors changes with overall density.
OIKOS,
77(1), 158-162.
Author URL.
Hack, M.A. Thompson, D.J. (1996). Relative success of unequal competitors changes with overall density. Oikos, 77, 158-162.
Tregenza, T. (1995). Building on the ideal free distribution. Adv.Ecol.Res, 26, 253-302.
TREGENZA T (1995). DREAM TEAMS.
NEW SCIENTIST,
148(2000), 59-59.
Author URL.
Tregenza, T. Parker, G.A. Harvey, I.F. (1995). Evolutionarily stable foraging speeds in feeding scrambles: a model and an experimental test. Proceedings of the Royal Society B, 260, 273-277.
Tregenza, T. (1994). Common misconceptions in applying the ideal free distribution. Animal Behaviour, 47, 485-487.
Chapters
Tregenza, T. (2007). Mimicry as deceptive resemblance: beyond the one-trick ponies. In Dautenhahnand K, Nehaniv CL (Eds.)
Imitation and Social Learning in Robots, Humans and Animals: Behavioural, Social and Communicative Dimensions, Cambridge: Cambridge University Press, 441-453.
Author URL.
Ritchie MG (2007). Sexual selection and speciation. In (Ed)
ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS, 79-102.
Author URL.
Tregenza T & Butlin RK (1999). Genetic diversity: Do marker genes tell us the whole story?. In Magurran AE, May RM (Eds.) Evolution of Biological Diversity, 37-55.
Conferences
Christmas JT, Everson RM, Rodriguez-Munoz R, Tregenza T (2013). Variational Bayesian Tracking: Whole Track Convergence for Large Scale Ecological Video Monitoring. IEEE International Joint Conference on Neural Networks (IJCNN). 5th - 9th Aug 2013.
Christmas J, Everson R, Rodriguez-Munoz R, Tregenza T (2013). Variational Bayesian Tracking: Whole Track Convergence for Large-scale Ecological Video Monitoring.
Author URL.
Publications by year
In Press
Cornell S, Tregenza T (In Press). A new theory for the evolution of polyandry. Proceedings of the Royal Society B: Biological Sciences
Price N, Green S, Troscianko J, Tregenza T, Stevens M (In Press). Background matching and disruptive coloration as habitat-specific strategies for camouflage. Scientific Reports
Carter EE, Tregenza T, Stevens M (In Press). Ship noise inhibits colour change, camouflage, and anti-predator behaviour in shore crabs. Current Biology
2023
Rodríguez-Muñoz R, Hopwood P, Boonekamp JJ, Edwards SA, Price TW, Rees J, Tregenza T (2023). Local adaptation does not constrain the expression of behaviour in translocated wild crickets.
Animal Behaviour,
200, 15-23.
Abstract:
Local adaptation does not constrain the expression of behaviour in translocated wild crickets
Behaviour has the potential to retard evolutionary adaptation by equipping animals with the capacity to radically change their interactions with the environment without evolving. Despite this potential for plasticity, laboratory studies frequently identify among-population differences in responses to identical stimuli, suggesting that genetic adaption often reduces behavioural flexibility. However, laboratory environments are typically far removed from nature, so their relevance to the variation we might expect to see in the wild (either among environments or as a result of changes in climate) is unclear. This is a particularly acute issue in relation to behaviour because behaving in an optimal fashion requires animals to receive and process complex sensory information which may be disrupted by laboratory conditions. We translocated newly adult male field crickets, Gryllus campestris, from five high-altitude and five low-altitude populations into a single low-altitude meadow from which we had removed all naturally present males. By tagging every individual and employing a network of 140 video cameras we were able to record comprehensive behavioural information from early adulthood until death. This allowed us to directly compare the behaviour of individuals from populations known to be genetically divergent and adapted to either high or low altitudes. We found very limited evidence for an effect on behaviour of the altitudinal environment in which crickets had evolved and developed, despite the large scale of our study (>20 000 h of observations of 128 males). Our findings suggests that when provided with all the environmental cues present in their natural environment, local adaptation does not lead to substantial constraints on behaviour. This supports the hypothesis that the potential flexibility of behaviour may tend to reduce selection for local adaptation.
Abstract.
Wilde JA, Rodríguez-Muñoz R, Darden SK, Tregenza T, Fawcett TW (2023). Signalling males increase or decrease their calling effort according to the proximity of rivals in a wild cricket.
Animal Behaviour,
203, 53-61.
Abstract:
Signalling males increase or decrease their calling effort according to the proximity of rivals in a wild cricket
Males that employ dynamic courtship displays to attract females may tactically adjust their courtship in response to their social environment. However, we know little about how sexual signals are adjusted in complex natural settings, where individuals are competing for attention against a backdrop of signals from nearby and distant rivals. We investigated this using data from the WildCrickets project, a wild population of field crickets, Gryllus campestris, continuously monitored via CCTV cameras. We used over a million scan samples from 129 males across 51 days to explore how the singing and proximity of other males influenced male singing behaviour. We first quantified the spatial network of the males to understand how the extent of singing overlap is affected by the distance between them, and found a moderate overlap across the whole population, regardless of distance. We then used a finer-grained analysis controlling for the effect of environmental variables. At distances greater than 1 m, we found a stimulatory effect of singing by other males on a focal male's singing behaviour, leading to males singing in the same time intervals. The overlap in singing became weaker as the distance between males increased. Conversely, we found that males were less likely to call when another male was singing very close by (within 1 m), suggesting an inhibitory effect. These findings reveal how, in a dynamic social network in a wild population, males perform fine-scale adjustments to their signalling behaviour in response to signalling by other males both nearby and far away.
Abstract.
2022
Aagaard A, Liu S, Tregenza T, Braad Lund M, Schramm A, Verhoeven KJF, Bechsgaard J, Bilde T (2022). Adapting to climate with limited genetic diversity: Nucleotide, DNA methylation and microbiome variation among populations of the social spider Stegodyphus dumicola.
Mol Ecol,
31(22), 5765-5783.
Abstract:
Adapting to climate with limited genetic diversity: Nucleotide, DNA methylation and microbiome variation among populations of the social spider Stegodyphus dumicola.
Understanding the role of genetic and nongenetic variants in modulating phenotypes is central to our knowledge of adaptive responses to local conditions and environmental change, particularly in species with such low population genetic diversity that it is likely to limit their evolutionary potential. A first step towards uncovering the molecular mechanisms underlying population-specific responses to the environment is to carry out environmental association studies. We associated climatic variation with genetic, epigenetic and microbiome variation in populations of a social spider with extremely low standing genetic diversity. We identified genetic variants that are associated strongly with environmental variation, particularly with average temperature, a pattern consistent with local adaptation. Variation in DNA methylation in many genes was strongly correlated with a wide set of climate parameters, thereby revealing a different pattern of associations than that of genetic variants, which show strong correlations to a more restricted range of climate parameters. DNA methylation levels were largely independent of cis-genetic variation and of overall genetic population structure, suggesting that DNA methylation can work as an independent mechanism. Microbiome composition also correlated with environmental variation, but most strong associations were with precipitation-related climatic factors. Our results suggest a role for both genetic and nongenetic mechanisms in shaping phenotypic responses to local environments.
Abstract.
Author URL.
Tregenza T, Niemelä PT, Rodríguez-Muñoz R, Hopwood PE (2022). Environment and mate attractiveness in a wild insect.
Behavioral Ecology,
33(5), 999-1006.
Abstract:
Environment and mate attractiveness in a wild insect
AbstractThe role of female choice in sexual selection is well established, including the recognition that females choose their mates based on multiple cues. These cues may include intrinsic aspects of a male’s phenotype as well as aspects of the environment associated with the male. The role of the spatial location of a potential mate has been well studied in territorial vertebrates. However, despite their role as laboratory models for studies of sexual selection, the potential for insects to choose their mates on the basis of location has scarcely been studied. We studied a natural population of individually tagged crickets (Gryllus campestris) in a meadow in Northern Spain. Adults typically move between burrows every few days, allowing us to examine how pairing success of males can be predicted by the burrow they occupy, independent of their own characteristics. We observed the entirety of ten independent breeding seasons to provide replication and to determine whether the relative importance of these factors is stable across years. We find that both male ID and the ID his burrow affect the likelihood that he is paired with a female, but the burrow has a consistently greater influence. Furthermore, the two factors interact: the relative attractiveness of an individual male depends on which burrow he occupies. Our finding demonstrates a close interaction between naturally and sexually selected traits. It also demonstrates that mate choice studies may benefit from considering not only obvious secondary sexual traits, but also more cryptic traits such as microhabitat choice.
Abstract.
Boonekamp J, Rodríguez-Muñoz R, Hopwood P, Zuidersma E, Mulder E, Wilson A, Verhulst S, Tregenza T (2022). Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets.
Mol Ecol,
31(23), 6128-6140.
Abstract:
Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets.
Many organisms are capable of growing faster than they do. Restrained growth rate has functionally been explained by negative effects on lifespan of accelerated growth. However, the underlying mechanisms remain elusive. Telomere attrition has been proposed as a causal agent and has been mostly studied in endothermic vertebrates. We established that telomeres exist as chromosomal-ends in a model insect, the field cricket Gryllus campestris, using terminal restriction fragment and Bal 31 methods. Telomeres comprised TTAGGn repeats of 38 kb on average, more than four times longer than the telomeres of human infants. Bal 31 assays confirmed that telomeric repeats were located at the chromosome-ends. We tested whether rapid growth between day 1, day 65, day 85, and day 125 is achieved at the expense of telomere length by comparing nymphs reared at 23°C with their siblings reared at 28°C, which grew three times faster in the initial 65 days. Surprisingly, neither temperature treatment nor age affected average telomere length. Concomitantly, the broad sense heritability of telomere length was remarkably high at ~100%. Despite high heritability, the evolvability (a mean-standardized measure of genetic variance) was low relative to that of body mass. We discuss our findings in the context of telomere evolution. Some important features of vertebrate telomere biology are evident in an insect species dating back to the Triassic. The apparent lack of an effect of growth rate on telomere length is puzzling, suggesting strong telomere length maintenance during the growth phase. Whether such maintenance of telomere length is adaptive remains elusive and requires further study investigating the links with fitness in the wild.
Abstract.
Author URL.
2021
Tregenza T, Rodríguez-Muñoz R, Boonekamp JJ, Hopwood PE, Sørensen JG, Bechsgaard J, Settepani V, Hegde V, Waldie C, May E, et al (2021). Evidence for genetic isolation and local adaptation in the field cricket Gryllus campestris.
J Evol Biol,
34(10), 1624-1636.
Abstract:
Evidence for genetic isolation and local adaptation in the field cricket Gryllus campestris.
Understanding how species can thrive in a range of environments is a central challenge for evolutionary ecology. There is strong evidence for local adaptation along large-scale ecological clines in insects. However, potential adaptation among neighbouring populations differing in their environment has been studied much less. We used RAD sequencing to quantify genetic divergence and clustering of ten populations of the field cricket Gryllus campestris in the Cantabrian Mountains of northern Spain, and an outgroup on the inland plain. Our populations were chosen to represent replicate high and low altitude habitats. We identified genetic clusters that include both high and low altitude populations indicating that the two habitat types do not hold ancestrally distinct lineages. Using common-garden rearing experiments to remove environmental effects, we found evidence for differences between high and low altitude populations in physiological and life-history traits. As predicted by the local adaptation hypothesis, crickets with parents from cooler (high altitude) populations recovered from periods of extreme cooling more rapidly than those with parents from warmer (low altitude) populations. Growth rates also differed between offspring from high and low altitude populations. However, contrary to our prediction that crickets from high altitudes would grow faster, the most striking difference was that at high temperatures, growth was fastest in individuals from low altitudes. Our findings reveal that populations a few tens of kilometres apart have independently evolved adaptations to their environment. This suggests that local adaptation in a range of traits may be commonplace even in mobile invertebrates at scales of a small fraction of species' distributions.
Abstract.
Author URL.
Pincheira-Donoso D, Harvey LP, Grattarola F, Jara M, Cotter SC, Tregenza T, Hodgson DJ (2021). The multiple origins of sexual size dimorphism in global amphibians.
Global Ecology and Biogeography,
30(2), 443-458.
Abstract:
The multiple origins of sexual size dimorphism in global amphibians
Aim: Body size explains most of the variation in fitness within animal populations and is therefore under constant selection from ecological and reproductive pressures, which often promote its evolution in sex-specific directions, leading to sexual size dimorphism (SSD). Several hypotheses have been proposed to explain the vast diversity of SSD across species. These hypotheses emphasize: (a) the mate competition benefits to larger male size (sexual selection); (b) the benefits of larger female size for fecundity (fecundity selection); (c) the simultaneous benefits of niche divergence for males and females to reduce intersexual competition for ecological resources (natural selection); and (d) the underlying impact of geographical variation in climatic pressures expected to shape large-scale patterns of SSD in synergy with the above selection pressures (e.g. intensification of fecundity selection as breeding seasons shorten). Based on a new, global-scale amphibian dataset, we address the shortage of large-scale, integrative tests of these four hypotheses. Location: Global. Time period: Extant. Major taxa studied: Class Amphibia. Methods: Using a > 3,500 species dataset spanning body size, ecological, life-history, geographical and climatic data, we performed phylogenetic linear models to address the sexual, fecundity, ecological and climatic hypotheses of SSD. Results: Evolution of SSD is discordant between anurans and salamanders. Anuran SSD is shaped by climate (male-biased SSD increases with temperature seasonality) and by nesting site. In salamanders, SSD converges across species that occupy the same types of microhabitats (“ecodimorphs”), whereas reproductive or climatic pressures have no effects on their SSD. These contrasts are associated with latitudinal gradients of SSD in anurans, but not in salamanders. Main conclusions: Amphibian SSD is driven by ecological and climatic pressures, whereas no roles for sexual or fecundity selection were detected. We show that macroevolutionary processes determined by different forms of selection lead to latitudinal patterns of trait diversity, and the lack of them.
Abstract.
2020
Zhou J, Zhang J, Tregenza T, Pan Y, Wang Q, Shi H, Liu X (2020). Larval Host Preference and Suitability for the Sawfly Mesoneura rufonota among Five Cinnamomun Tree Species.
Insects,
11(2).
Abstract:
Larval Host Preference and Suitability for the Sawfly Mesoneura rufonota among Five Cinnamomun Tree Species.
The camphor sawfly, Mesoneura rufonota Rohwer, is an economically important leaf-chewing pest of the genus Cinnamomum Trew. However, little is known about the range of species that it can infest within this genus or whether larvae show preferences for particular species. We conducted preference and performance experiments under laboratory conditions to assess larval host preference and suitability as a host plant of five congeneric trees species: C. camphora (Linn) Presl, C. bodinieri Levl. C. burmanni (Nees et T. Nees) Blume, C. pauciflorum Nees, and C. micranthum (Hay.) Hay. In no-choice, two-choice and multiple-choice feeding trials, significantly higher feeding rates were found on C. camphora, followed by C. bodinieri, compared to those on the other three tree species. In two-choice behavior trials, larvae moved to occupy leaves of C. camphora faster and more frequently, followed by C. bodinieri, than when offered the other three tree species. In no-choice fitness trials, the survival of larval and pupal stage was the highest, the developmental duration of larval and pupal stage was the shortest, the pupal body weight was the heaviest and adults lived the longest on C. camphora followed by C. bodinieri, while M. rufonota did not complete development on C. burmanni, C. pauciflorum or C. micranthum. Our results demonstrate that larvae consistently prefer and perform better on C. camphora leaves, that they can utilize C. bodinieri, but it is less preferred, and that C. burmanni, C. pauciflorum, and C. micranthum appear to be unsuitable as a host for M. rufonota.
Abstract.
Author URL.
Tregenza T, Rodríguez-Muñoz R (2020). Makai et al Animal Behaviour 2020 datasets on feeding, fleeing and movement.
Abstract:
Makai et al Animal Behaviour 2020 datasets on feeding, fleeing and movement
The dataset includes three files:. (1) data on individual cricket movement in/out the burrow, (2) data on time spent feeding during each individual observation period and (3) data on time taken for the cricket to move outside the burrow after a fleeing event. The names of the variable in each of the files is self-explanatory.
Abstract.
Tregenza T, Rodríguez-Muñoz R (2020). Makai et al Animal Behaviour 2020 paper dataset1.
Makai G, Rodríguez-Muñoz R, Boonekamp JJ, Hopwood P, Tregenza T (2020). Males and females differ in how their behaviour changes with age in wild crickets.
Animal Behaviour,
164, 1-8.
Abstract:
Males and females differ in how their behaviour changes with age in wild crickets
Because females produce and lay eggs or nurture embryos, they are constrained in the timing of their investment in reproduction. Males may have more opportunity to concentrate reproductive investment earlier in life, mating with as many females as possible soon after becoming adult. This fundamental difference leads to the prediction that because males can bias allocation towards increased reproductive investment early in life, they will use up resources earlier in their lives and hence senesce faster than females. A first step towards testing this prediction is to determine whether there are between-sex differences in age-related changes in behaviour. To do this we recorded the behaviour of crickets, Gryllus campestris, in a natural population living in and around their burrows in a meadow in northern Spain. Following individuals of both sexes through their adult lives, we recorded a range of nonreproductive behaviours, including how often they moved in and out of their burrows, how long they spent at the entrance, how long they spent outside, how quickly they left a burrow after fleeing inside to escape predation and whether they fed. We found evidence for substantial age-related changes in two of the movement traits in males, but not in females. Males moved less often and spent less time outside their burrows as they aged, whereas females showed no age-related changes in either trait. Feeding was not affected by age in males, but females fed more often as they got older. Our findings are consistent with the prediction that males senesce faster than females; experiments in nature will be needed to determine whether this pattern arises from life history trade-offs between reproduction and other traits.
Abstract.
Boonekamp J, Rodríguez-Muñoz R, Hopwood P, Zuidersma E, Mulder E, Wilson A, Verhulst S, Tregenza T (2020). Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets.
Abstract:
Telomere length is highly heritable and independent of growth rate manipulated by temperature in field crickets
AbstractMany organisms are capable of growing faster than they do. Restrained growth rate has functionally been explained by negative effects on lifespan of accelerated growth. However, the underlying mechanisms remain elusive. Telomere attrition has been proposed as a causal agent and has been studied in endothermic vertebrates. We established that telomeres exist as chromosomal-ends in a model insect, the field cricket, using terminal restriction fragment andBal 31methods. Telomeres comprised TTAGGn repeats of 38kb on average, more than four times longer than the telomeres of human infants.Bal 31assays confirmed that telomeric repeats were located at the chromosome-ends. We tested whether rapid growth is achieved at the expense of telomere length by comparing crickets reared at 23°C with their siblings reared at 28°C, which grew three times faster. Surprisingly, neither temperature treatment nor age affected average telomere length. Concomitantly, the broad sense heritability of telomere length was remarkably high at ~100%. Despite high heritability, the evolvability (a mean standardized measure of genetic variance) was low relative to that of body mass. We discuss the different interpretations of these scaling methods in the context of telomere evolution. It is clear that some important features of vertebrate telomere biology are evident in an insect species dating back to the Triassic, but also that there are some striking differences. The apparent lack of an effect of growth rate and the total number of cell divisions on telomere length is puzzling, suggesting that telomere length could be actively maintained during the growth phase. Whether such maintenance of telomere length is adaptive remains elusive and requires further study investigating the links with fitness in the wild.
Abstract.
2019
Rodríguez-Muñoz R, Boonekamp JJ, Liu XP, Skicko I, Haugland Pedersen S, Fisher DN, Hopwood P, Tregenza T (2019). Comparing individual and population measures of senescence across 10 years in a wild insect population.
Evolution,
73(2), 293-302.
Abstract:
Comparing individual and population measures of senescence across 10 years in a wild insect population.
Declines in survival and performance with advancing age (senescence) have been widely documented in natural populations, but whether patterns of senescence across traits reflect a common underlying process of biological ageing remains unclear. Senescence is typically characterized via assessments of the rate of change in mortality with age (actuarial senescence) or the rate of change in phenotypic performance with age (phenotypic senescence). Although both phenomena are considered indicative of underlying declines in somatic integrity, whether actuarial and phenotypic senescence rates are actually correlated has yet to be established. Here we present evidence of both actuarial and phenotypic senescence from a decade-long longitudinal field study of wild insects. By tagging every individual and using continuous video monitoring with a network of up to 140 video cameras, we were able to record survival and behavioral data on an entire adult population of field crickets. This reveals that both actuarial and phenotypic senescence vary substantially across 10 annual generations. This variation allows us to identify a strong correlation between actuarial and phenotypic measures of senescence. Our study demonstrates age-related phenotypic declines reflected in population level mortality rates and reveals that observations of senescence in a single year may not be representative of a general pattern.
Abstract.
Author URL.
Carter E (2019). Consequences of ship noise for camouflage, anti-predation, and movement in crabs.
Abstract:
Consequences of ship noise for camouflage, anti-predation, and movement in crabs.
The marine environment is becoming increasingly polluted, with unprecedented levels of anthropogenic noise changing the marine soundscape. Mounting evidence shows that exposure to this noise can cause numerous adverse effects across taxa. However, invertebrates, juveniles, and behaviours not dependent on acoustics have received relatively little attention. Furthermore, research into how individuals may cope with these pressures is lacking. I address these knowledge gaps through a series of laboratory-based playback experiments focussed on juvenile shore crabs (Carcinus maenas), using three noise treatments: ship noise, ambient underwater sounds (control), and ambient underwater sounds played at the same amplitude as the ship treatment (loud control).
In chapter 2, I examined the effects of ship noise on brightness change; a strategy employed by juvenile shore crabs to increase their level of camouflage and reduce predation risk. Individuals were repeatedly exposed to one of the aforementioned noise treatments for 8 weeks. Photographs of individuals, taken regularly throughout, were analysed using a predator vision model to determine the level of brightness change and camouflage in an ecologically relevant context. Ship noise reduced the overall brightness change and camouflage, though it did not affect the change in brightness per moult. The level of growth per moult was reduced by ship noise however, and the timing of moulting events was delayed. In chapter 3 I investigated the effects of noise on antipredator behaviour (using the response to a simulated predator) and locomotion, including the frequency of pausing and directionality of movement. By comparing the effects between individuals with varying levels of previous noise exposure, I also tested for signs of acclimatisation. Ship noise reduced the likelihood of individuals responding to a predator and increased their latency of response. Locomotion was not disrupted, but individuals moved away from ship noise, positioning themselves in quieter areas. These findings were consistent for all individuals, regardless of their previous level of noise exposure.
The negative consequences of anthropogenic noise in the marine environment are clearly not constrained to species or behaviours reliant on acoustics, as juvenile shore crabs exposed to ship noise suffered decreased levels of camouflage and reduced growth. Individuals also displayed maladaptive behavioural responses to a simulated predator when exposed to ship noise. There is no evidence that acclimatisation occurred, but individuals did attempt to physically avoid noisy areas. Loud natural sounds did not affect any behaviours studied, suggesting the type of noise is important in determining how individuals may be affected. Overall, this thesis shows that juvenile shore crabs suffer multiple negative effects from noise pollution, including the disruption of critical behaviours that are pervasive in the marine environment, with potential implications for survival.
Abstract.
Dutta R, Reddy M, Tregenza T (2019). Discovery of an acoustically locating parasitoid with a potential role in divergence of song types among sympatric populations of the bush cricket Mecopoda elongata.
Journal of Orthoptera Research,
28(2), 181-186.
Abstract:
Discovery of an acoustically locating parasitoid with a potential role in divergence of song types among sympatric populations of the bush cricket Mecopoda elongata
The bush cricket Mecopoda elongata provides a striking example of sympatric intraspecific divergence in mating signals. Five completely distinct song types are found in various parapatric and sympatric locations in South India. While there is convincing evidence that population divergence in M. elongata is being maintained as a result of divergence in acoustic signals, cuticular chemical profiles, and genital characters, the causes of the evolution of such divergence in the first place are unknown. We describe the discovery of a tachinid parasitoid with an orthopteroid hearing mechanism affecting M. elongata. This parasitoid may have a role in driving the extraordinary divergence that had occurred among M. elongata song types. Over two years we sampled individuals of three sympatric song types in the wild and retained individuals in captivity to reveal rates of parasitization. We found that all three song types were infected with the parasitoid but that there were significant differences among song types in their probability of being infected. The probability of tachinid parasitization also differed between the two sampling periods. Therefore, it is possible that parasitoid infection plays a role in song type divergence among sympatric bush cricket populations.
Abstract.
Fisher DN, Rodríguez-Muñoz R, Tregenza T (2019). Dynamic networks of fighting and mating in a wild cricket population.
Animal Behaviour,
155, 179-188.
Abstract:
Dynamic networks of fighting and mating in a wild cricket population
Reproductive success is often highly skewed in animal populations. Yet the processes leading to this are not always clear. Similarly, connections in animal social networks are often nonrandomly distributed, with some individuals with many connections and others with few, yet whether there are simple explanations for this pattern has not been determined. Numerous social interactions involve dyads embedded within a wider network. As a result, it may be possible to model which individuals accumulate social interactions through a more general understanding of the social network's structure, and how this structure changes over time. We analysed fighting and mating interactions across the breeding season in a population of wild field crickets under surveillance from a network of video cameras. We fitted stochastic actor-oriented models to determine the dynamic process by which networks of cricket fighting and mating interactions form, and how they co-influence each other. We found crickets tended to fight those in close spatial proximity to them and those possessing a mutual connection in the fighting network, and heavier crickets fought more often. We also found that crickets that mated with many others tended to fight less in the following time period. This demonstrates that a mixture of spatial constraints, characteristics of individuals and characteristics of the immediate social environment are key for determining social interactions. The mating interaction network required very few parameters to understand its growth and thus its structure; only homophily by mating success was required to simulate the skew of mating interactions seen in this population. This demonstrates that relatively simple, but dynamic, processes can give highly skewed distributions of mating success.
Abstract.
Rodríguez-Muñoz R, Hopwood P, Fisher D, Skicko I, Tucker R, Woodcock K, Slate J, Walling C, Tregenza T (2019). Older males attract more females but get fewer matings in a wild field cricket.
Animal Behaviour,
153, 1-14.
Abstract:
Older males attract more females but get fewer matings in a wild field cricket
The age of potential mates has been proposed to be an important target for mate choice by females. Alternative hypotheses predict preferences in either direction. Females might be expected to prefer older males because such males have demonstrated their capacity to survive. Alternatively, they might prefer younger males that have not accumulated deleterious mutations. Preferences in both directions have been observed in laboratory experiments, suggesting that this is an issue that needs to be understood within its ecological context. We measured individual behaviour and reproductive success in a natural population of the field cricket Gryllus campestris over 10 years. We found that in this annual insect, a male's age relative to his peers was poorly correlated with his life span. This suggests that there is limited potential for selection to favour female choice for older males because a strategy of choosing older males would not significantly increase a female's likelihood of mating with a long-lived male. Older males were more successful at pairing up with females at a burrow, but once paired they were less likely to mate with them. By genotyping the next generation of adults we confirmed that observations of both pairing up with a female and matings were associated with successful offspring production. However, there was no relationship between how old a male was at mating and how many adult offspring he had. This lack of evidence for any fitness benefits to females from mate choice in relation to male age was consistent with the observation that the age of males had opposite effects on their success in pairing up with females compared to their success in mating with them.
Abstract.
Rodríguez-Muñoz R, Boonekamp JJ, Fisher D, Hopwood P, Tregenza T (2019). Slower senescence in a wild insect population in years with a more female-biased sex ratio.
Proc Biol Sci,
286(1900).
Abstract:
Slower senescence in a wild insect population in years with a more female-biased sex ratio.
Life-history theories of senescence are based on the existence of a trade-off in resource allocation between body maintenance and reproduction. This putative trade-off means that environmental and demographic factors affecting the costs of reproduction should be associated with changes in patterns of senescence. In many species, competition among males is a major component of male reproductive investment, and hence variation in the sex ratio is expected to affect rates of senescence. We test this prediction using nine years of demographic and behavioural data from a wild population of the annual field cricket Gryllus campestris. Over these generations, the sex ratio at adulthood varied substantially, from years with an equal number of each sex to years with twice as many females as males. Consistent with the predictions of theory, we found that in years with a greater proportion of females, both sexes experienced a slower increase in mortality rate with age. Additionally, phenotypic senescence in males was slower in years when there were more females. Sex ratio did not affect the baseline mortality rate in males, but females suffered higher age-independent mortality rates when males were in short supply.
Abstract.
Author URL.
Rodríguez-Muñoz R, Boonekamp JJ, Liu XP, Skicko I, Fisher DN, Hopwood P, Tregenza T (2019). Testing the effect of early-life reproductive effort on age-related decline in a wild insect.
Evolution,
73(2), 317-328.
Abstract:
Testing the effect of early-life reproductive effort on age-related decline in a wild insect.
The disposable soma theory of ageing predicts that when organisms invest in reproduction they do so by reducing their investment in body maintenance, inducing a trade-off between reproduction and survival. Experiments on invertebrates in the lab provide support for the theory by demonstrating the predicted responses to manipulation of reproductive effort or lifespan. However, experimental studies in birds and evidence from observational (nonmanipulative) studies in nature do not consistently reveal trade-offs. Most species studied previously in the wild are mammals and birds that reproduce over multiple discrete seasons. This contrasts with temperate invertebrates, which typically have annual generations and reproduce over a single season. We expand the taxonomic range of senescence study systems to include life histories typical of most temperate invertebrates. We monitored reproductive effort, ageing, and survival in a natural field cricket population over ten years to test the prediction that individuals investing more in early-reproduction senesce faster and die younger. We found no evidence of a trade-off between early-life reproductive effort and survival, and only weak evidence for a trade-off with phenotypic senescence. We discuss the possibility that organisms with multiple discrete breeding seasons may have greater opportunities to express trade-offs between reproduction and senescence.
Abstract.
Author URL.
Ørskov CK, Tregenza T, Overgaard J (2019). Using radiotelemetry to study behavioural thermoregulation in insects under field conditions.
Methods in Ecology and Evolution,
10(10), 1773-1782.
Abstract:
Using radiotelemetry to study behavioural thermoregulation in insects under field conditions
Thermoregulation is a central aspect of animal physiology. Mobile ectotherms have the potential to influence their temperature through their location and orientation. Behavioural thermoregulation has been extensively studied in insects, particularly in the migratory locust Locusta migratoria. However, most field studies are confined to daytime observations typically using invasive thermocouples with obvious potential to disrupt natural behaviour. We demonstrate that miniature radiotransmitters represent an alternative and less invasive method to study insect thermoregulation. We discuss how this method can be used to study the thermal behaviour of free-ranging animals for extended periods. Specifically, we show that there is a close correlation between temperature recordings from implanted thermocouples in locusts L. migratoria and externally mounted radiotransmitters on the same animals. Our experiments match earlier observations of locust thermoregulatory behaviour confirming that the locusts with transmitters exhibit ‘normal’ thermoregulatory responses to feeding and to infections (behavioural fever). Finally, we demonstrate the practicality of a radiotransmitter-based system by recording natural thermoregulatory behaviour of locusts in a semi-field setting. Our field study showed locusts actively chose warm microclimates during the day and cold microclimates at night. We conclude that the use of radiotelemetry in studies of behavioural thermoregulation in wild insects could provide unique continuous recordings of body temperature over several days. Such data will provide researchers with a more complete understanding of how insects use behavioural thermoregulation in nature.
Abstract.
2018
Dutta R, Balakrishnan R, Tregenza T (2018). Divergence in potential contact pheromones and genital morphology among sympatric song types of the bush cricket Mecopoda elongata.
Frontiers in Ecology and Evolution,
6(OCT).
Abstract:
Divergence in potential contact pheromones and genital morphology among sympatric song types of the bush cricket Mecopoda elongata
A well-established route to speciation in animals is via the evolution of divergent male mating signals and female preferences within a species. However, an open question is how common it is for near complete isolation to be achieved through a single signal-receiver system as opposed to multiple aspects of the mate-recognition system diverging simultaneously. The five highly divergent mate-attraction song types of the bush cricket Mecopoda elongata exemplify reproductive isolation in sympatry through long-distance mating signals. Female preference for their own song type has been established as a strong pre-mating reproductive barrier, but the potential existence of additional isolating mechanisms has not been investigated. We quantify divergence in cuticular lipid profiles and external genital structures between song types. These traits show significant variation among species of Orthoptera and are known to be used in mate recognition following contact. We show that divergence among sympatric Mecopoda song types in both cuticular lipid profiles and two external genital structures is sufficiently extensive that either of them can be used to identify individual song type with 90% accuracy. Our findings suggest that multiple isolating mechanisms are likely to evolve simultaneously facilitating a more robust reproductive isolation. Our study indicates a role for sexual selection in the divergence and potential future speciation of these populations and suggests that reproductive isolation may frequently evolve through simultaneous divergence across different aspects of mate recognition systems.
Abstract.
Fisher DN, David M, Rodriguez-Munoz R, Tregenza T (2018). Lifespan and age, but not residual reproductive value or condition, are related to behaviour in wild field crickets.
ETHOLOGY,
124(5), 338-346.
Author URL.
Pincheira-Donoso D, Tregenza T, Butlin RK, Hodgson DJ (2018). Sexes and species as rival units of niche saturation during community assembly.
Global Ecology and Biogeography,
27(5), 593-603.
Abstract:
Sexes and species as rival units of niche saturation during community assembly
Aim: Community assembly is traditionally assumed to result from speciation and colonization mediated by available niche space. This paradigm is expanded by the theory that niche space can also be saturated by intersexual adaptive divergence (ecological sexual dimorphism) when interspecific competition is relaxed. This theory (here termed ‘niche-packing equivalence’) predicts that the evolution of ecological sexual dimorphism constrains the ecological opportunity that would otherwise lead to ecological speciation or colonization, and that saturation of niches by different species constrains divergent selection for divergence between the sexes. Therefore, sexes and species are equivalent, yet antagonistic units of niche occupation. We present the most comprehensive test of the niche-packing equivalence theory at ecological time-scales (assemblage level) to date. Location: South America. Major taxa studied: Liolaemus lizards. Methods: We identified 23 Liolaemus assemblages varying in species richness and sexual size dimorphism (SSD), distributed across a wide environmental range. We used mixed effects models, permutation tests and Markov Chain Monte Carlo (MCMC) regressions to quantify the relationship between SSD and species richness. We then partitioned the body size niche dimension between the sexes and amongst species, and tested for non-overlapping body size distributions. We regressed SSD and species richness of each assemblage against environmental predictors, using multi-model inference and structural equation modelling. Results: Sexual dimorphism declines with increasing species richness, and a strong signal of tension between the two remains following phylogenetic control. This pattern is accompanied by evidence of constraints on body-size partitioning amongst species and between the sexes: the two units of niche saturation tend not to overlap. However, across assemblages, species richness and SSD correlate with different environmental variables, suggesting that their tension is context-specific. Main conclusions: Our evidence supports the prediction that sexual dimorphism and species richness are alternative outcomes of adaptive radiation. However, this antagonism is mediated by a suite of environmental predictors that influence dimorphism and species richness differentially.
Abstract.
2017
Fisher DN, Ilany A, Silk MJ, Tregenza T (2017). Analysing animal social network dynamics: the potential of stochastic actor‐oriented models.
Journal of Animal Ecology,
86(2), 202-212.
Abstract:
Analysing animal social network dynamics: the potential of stochastic actor‐oriented models
Summary
Animals are embedded in dynamically changing networks of relationships with conspecifics. These dynamic networks are fundamental aspects of their environment, creating selection on behaviours and other traits. However, most social network‐based approaches in ecology are constrained to considering networks as static, despite several calls for such analyses to become more dynamic.
There are a number of statistical analyses developed in the social sciences that are increasingly being applied to animal networks, of which stochastic actor‐oriented models (SAOMs) are a principal example. SAOMs are a class of individual‐based models designed to model transitions in networks between discrete time points, as influenced by network structure and covariates. It is not clear, however, how useful such techniques are to ecologists, and whether they are suited to animal social networks.
We review the recent applications of SAOMs to animal networks, outlining findings and assessing the strengths and weaknesses of SAOMs when applied to animal rather than human networks. We go on to highlight the types of ecological and evolutionary processes that SAOMs can be used to study.
SAOMs can include effects and covariates for individuals, dyads and populations, which can be constant or variable. This allows for the examination of a wide range of questions of interest to ecologists. However, high‐resolution data are required, meaning SAOMs will not be useable in all study systems. It remains unclear how robust SAOMs are to missing data and uncertainty around social relationships.
Ultimately, we encourage the careful application of SAOMs in appropriate systems, with dynamic network analyses likely to prove highly informative. Researchers can then extend the basic method to tackle a range of existing questions in ecology and explore novel lines of questioning.
Abstract.
Baxter SW, Hoffman JI, Tregenza T, Wedell N, Hosken DJ (2017). EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly.
Heredity (Edinb),
118(4), 322-329.
Abstract:
EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly.
Understanding selection in the wild remains a major aim of evolutionary ecology and work by Ford and colleagues on the meadow brown butterfly Maniola jurtina did much to ignite this agenda. A great deal of their work was conducted during the 1950s on the Isles of Scilly. They documented island-specific wing-spot patterns that remained consistent over about a decade, but patterns on some islands changed after environmental perturbation. It was suggested that these wing-spot patterns reflected island-specific selection and that there was little migration between islands. However, genetic studies to test the underlying assumption of restricted migration are lacking and it is also unknown whether the originally described wing-spot patterns have persisted over time. We therefore collected female butterflies from five of Ford's original study locations, including three large islands (St Mary's, St Martin's and Tresco) and two small islands (Tean and St Helen's). Wing-spot patterns had not changed appreciably over time on three of the islands (two large and one small), but were significantly different on the other two. Furthermore, analysis of 176 amplified fragment length polymorphisms revealed significant genome-wide differentiation among the five islands. Our findings are consistent with Ford's conclusions that despite the close proximity of these islands, there is restricted gene flow among them.
Abstract.
Author URL.
Dutta R, Tregenza T, Balakrishnan R (2017). Reproductive isolation in the acoustically divergent groups of tettigoniid, Mecopoda elongata.
PLoS One,
12(11).
Abstract:
Reproductive isolation in the acoustically divergent groups of tettigoniid, Mecopoda elongata.
Sympatric divergent populations of the same species provide an opportunity to study the evolution and maintenance of reproductive isolation. Male mating calls are important in sexual selection in acoustically communicating species, and they also have the potential to maintain isolation among species or incipient species. We studied divergent south Indian populations of the bush cricket Mecopoda elongata which are extremely difficult to distinguish morphologically, but which exhibit striking divergence in male acoustic signals. We performed phonotactic experiments investigating the relative preference of females of the "Chirper" song type for calls of all 5 of the song types found in the region (in varying degrees of sympatry). We found that Chirper females preferred their own song type and were completely unresponsive to three trilling song types. Chirper females were occasionally attracted to the call type "Double Chirper" (the call most similar to their own type), suggesting call preference alone cannot provide a complete isolating mechanism. To investigate the basis of call preference we investigated the response of chirper females to variation in chirp rate. Chirper females responded most frequently to a mean chirp rate characteristic of their own song type rather than a higher chirp rate which would be more characteristic of the Double-Chirper song type. This suggests females drive stabilising selection on male chirp rate, which may contribute to the maintenance of isolation. Finally, a no-choice mating experiment using Chirper females and Chirper and Double Chirper males revealed a significant preference of Chirper females to mate with their own song type, even without a requirement for phonotaxis. Overall, the strong specificity of Chirper females for their 'own' song type provides evidence for behavioural isolation among divergent sympatric Mecopoda song types being maintained by female preference for both male song type and subsequent mating probability driven by other cues.
Abstract.
Author URL.
2016
Fisher DN, Rodríguez-Muñoz R, Tregenza T (2016). Comparing pre- and post-copulatory mate competition using social network analysis in wild crickets.
Behav Ecol,
27(3), 912-919.
Abstract:
Comparing pre- and post-copulatory mate competition using social network analysis in wild crickets.
Sexual selection results from variation in success at multiple stages in the mating process, including competition before and after mating. The relationship between these forms of competition, such as whether they trade-off or reinforce one another, influences the role of sexual selection in evolution. However, the relationship between these 2 forms of competition is rarely quantified in the wild. We used video cameras to observe competition among male field crickets and their matings in the wild. We characterized pre- and post-copulatory competition as 2 networks of competing individuals. Social network analysis then allowed us to determine 1) the effectiveness of precopulatory competition for avoiding postcopulatory competition, 2) the potential for divergent mating strategies, and 3) whether increased postcopulatory competition reduces the apparent reproductive benefits of male promiscuity. We found 1) limited effectiveness of precopulatory competition for avoiding postcopulatory competition; 2) males do not specifically engage in only 1 type of competition; and 3) promiscuous individuals tend to mate with each other, which will tend to reduce variance in reproductive success in the population and highlights the trade-off inherent in mate guarding. Our results provide novel insights into the works of sexual competition in the wild. Furthermore, our study demonstrates the utility of using network analyses to study competitive interactions, even in species lacking obvious social structure.
Abstract.
Author URL.
Hopwood PE, Moore AJ, Tregenza T, Royle NJ (2016). Erratum to Male burying beetles extend, not reduce, parental care duration when reproductive competition is high [J. Evol. Biol. 28: 1394-1402]. Journal of Evolutionary Biology, 29(1).
Lane SM, Haughan AE, Evans D, Tregenza T, House CM (2016). Same-sex sexual behaviour as a dominance display.
Animal Behaviour,
114, 113-118.
Abstract:
Same-sex sexual behaviour as a dominance display
Same-sex sexual behaviour (SSB) is widespread across taxa. One adaptive hypothesis to explain the occurrence and maintenance of SSB is that it acts to intensify or diminish aggression by providing males with a means to reinforce or resolve dominance. However, evidence for this hypothesis is very limited across taxa and the possibility that SSB acts as an extension of intrasexual competition remains contentious. We investigated the role of SSB in intensifying or diminishing aggression in the broad-horned flour beetle, Gnatocerus cornutus. We tested the hypothesis that SSB is an extension of male-male competition by observing how the occurrence of SSB and the stability of SSB courtship roles (i.e. whether males switched between mounting and being mounted) influenced levels of aggression within pairs. We found that, typically, males rapidly establish fixed SSB roles and moreover that the occurrence of SSB and the stability of SSB roles had a highly significant effect on levels of aggression observed within pairs. Pairs in which one male consistently mounted the other showed significantly lower levels of aggression than pairs in which neither male exhibited SSB or in which males continuously switched SSB roles and attempted to mount each other. Furthermore, males that were consistently on the receiving end of SSB demonstrated lower propensity to court females and had a lower mating success than active males. This pattern was analogous to that found in loser males as a result of fighting. Males that lost fights also courted less and had lower mating success than males that won fights. Our findings provide the first empirical support for the hypothesis that SSB is an extension of male-male competition. Furthermore, our results suggest that SSB may act as a display, allowing males to resolve dominance hierarchies without escalating into an injurious fight.
Abstract.
Lane SM, Dickinson AW, Tregenza T, House CM (2016). Sexual Selection on male cuticular hydrocarbons via male–male competition and female choice.
Journal of Evolutionary Biology,
29(7), 1346-1355.
Abstract:
Sexual Selection on male cuticular hydrocarbons via male–male competition and female choice
AbstractTraditional views of sexual selection assumed that male–male competition and female mate choice work in harmony, selecting upon the same traits in the same direction. However, we now know that this is not always the case and that these two mechanisms often impose conflicting selection on male sexual traits. Cuticular hydrocarbons (CHCs) have been shown to be linked to both social dominance and male attractiveness in several insect species. However, although several studies have estimated the strength and form of sexual selection imposed on male CHCs by female mate choice, none have established whether these chemical traits are also subject to sexual selection via male–male competition. Using a multivariate selection analysis, we estimate and compare sexual selection exerted by male–male competition and female mate choice on male CHC composition in the broad‐horned flour beetle Gnatocerus cornutus. We show that male–male competition exerts strong linear selection on both overall CHC abundance and body size in males, while female mate choice exerts a mixture of linear and nonlinear selection, targeting not just the overall amount of CHCs expressed but the relative abundance of specific hydrocarbons as well. We discuss the potential implications of this antagonistic selection with regard to male reproductive success.
Abstract.
Hopwood PE, Moore AJ, Tregenza T, Royle NJ (2016). The effect of size and sex ratio experiences on reproductive competition in <i>Nicrophorus vespilloides</i> burying beetles in the wild.
Journal of Evolutionary Biology,
29(3), 541-550.
Abstract:
The effect of size and sex ratio experiences on reproductive competition in Nicrophorus vespilloides burying beetles in the wild
AbstractMale parents face a choice: should they invest more in caring for offspring or in attempting to mate with other females? the most profitable course depends on the intensity of competition for mates, which is likely to vary with the population sex ratio. However, the balance of pay‐offs may vary among individual males depending on their competitive prowess or attractiveness. We tested the prediction that sex ratio and size of the resource holding male provide cues regarding the level of mating competition prior to breeding and therefore influence the duration of a male's biparental caring in association with a female. Male burying beetles, Nicrophorus vespilloides were reared, post‐eclosion, in groups that differed in sex ratio. Experimental males were subsequently translocated to the wild, provided with a breeding resource (carcass) and filmed. We found no evidence that sex ratio cues prior to breeding affected future parental care behaviour but males that experienced male‐biased sex ratios took longer to attract wild mating partners. Smaller males attracted a higher proportion of females than did larger males, securing significantly more monogamous breeding associations as a result. Smaller males thus avoided competitive male–male encounters more often than larger males. This has potential benefits for their female partners who avoid both intrasexual competition and direct costs of higher mating frequency associated with competing males.
Abstract.
Fisher DN, Rodríguez-Muñoz R, Tregenza T (2016). Wild cricket social networks show stability across generations. BMC Evolutionary Biology, 16(1).
2015
Fisher DN, James A, Rodríguez-Muñoz R, Tregenza T (2015). Behaviour in captivity predicts some aspects of natural behaviour, but not others, in a wild cricket population.
Proc Biol Sci,
282(1809).
Abstract:
Behaviour in captivity predicts some aspects of natural behaviour, but not others, in a wild cricket population.
Examining the relevance of 'animal personality' involves linking consistent among- and within-individual behavioural variation to fitness in the wild. Studies aiming to do this typically assay personality in captivity and rely on the assumption that measures of traits in the laboratory reflect their expression in nature. We examined this rarely tested assumption by comparing laboratory and field measurements of the behaviour of wild field crickets (Gryllus campestris) by continuously monitoring individual behaviour in nature, and repeatedly capturing the same individuals and measuring their behaviour in captivity. We focused on three traits that are frequently examined in personality studies: shyness, activity and exploration. All of them showed repeatability in the laboratory. Laboratory activity and exploration predicted the expression of their equivalent behaviours in the wild, but shyness did not. Traits in the wild were predictably influenced by environmental factors such as temperature and sunlight, but only activity showed appreciable within-individual repeatability. This suggests that some behaviours typically studied as personality traits can be accurately assayed in captivity, but the expression of others may be highly context-specific. Our results highlight the importance of validating the relevance of laboratory behavioural assays to analogous traits measured in the wild.
Abstract.
Author URL.
Tyler F, Fisher D, d'Ettorre P, Rodríguez-Muñoz R, Tregenza T (2015). Chemical cues mediate species recognition in field crickets.
Frontiers in Ecology and Evolution,
3(MAY).
Abstract:
Chemical cues mediate species recognition in field crickets
Cuticular hydrocarbons (CHCs) are important in mate choice in many insects, and may be used for species recognition if CHC profiles differ between potentially hybridizing species. In the sibling field cricket species Gryllus campestris and G. bimaculatus, females of G. bimaculatus are tolerant toward G. campestris males and can mate with them. However, G. campestris females are highly aggressive toward heterospecific G. bimaculatus males, and matings between them never happen. We examined whether cricket females might use CHCs to determine the species identity of their potential mates. We firstly analyzed the cuticular chemical profile by gas chromatography and mass spectrometry to assess the potential of CHCs to be used for species recognition in these crickets. We then manipulated females' ability to detect chemical cues by carrying out chemical ablation of the antennae, and measured changes in aggressive responses to heterospecific males. We show that there are significant interspecies differences in CHC expression for both sexes, and that females with chemically ablated antennae reduce aggressive behavior toward heterospecific males. Our findings support the prediction that cuticular semiochemicals can play a key role in reproductive isolation between closely related insect species.
Abstract.
Fisher DN, David M, Tregenza T, Rodríguez-Muñoz R (2015). Dynamics of among-individual behavioral variation over adult lifespan in a wild insect.
Behav Ecol,
26(4), 975-985.
Abstract:
Dynamics of among-individual behavioral variation over adult lifespan in a wild insect.
Investigating patterns of among and within-individual trait variation in populations is essential to understanding how selection shapes phenotypes. Behavior is often the most flexible aspect of the phenotype, and to understand how it is affected by selection, we need to examine how consistent individuals are. However, it is not well understood whether among-individual differences tend to remain consistent over lifetimes, or whether the behavior of individuals relative to one another varies over time. We examined the dynamics of 4 behavioral traits (tendency to leave a refuge, shyness, activity, and exploration) in a wild population of field crickets (Gryllus campestris). We tagged individuals and then temporarily removed them from their natural environment and tested them under laboratory conditions. All 4 traits showed among-individual variance in mean levels of expression across the adult lifespan, but no significant differences in how rapidly expression changed with age. For all traits, among-individual variance increased as individuals got older. Our findings reveal seldom examined changes in variance components over the adult lifetime of wild individuals. Such changes will have important implications for the relationship between behavioral traits, life-histories, and fitness and the consequences of selection on wild individuals.
Abstract.
Author URL.
Hopwood PE, Moore AJ, Tregenza T, Royle NJ (2015). Male burying beetles extend, not reduce, parental care duration when reproductive competition is high.
J Evol Biol,
28(7), 1394-1402.
Abstract:
Male burying beetles extend, not reduce, parental care duration when reproductive competition is high.
Male parents spend less time caring than females in many species with biparental care. The traditional explanation for this pattern is that males have lower confidence of parentage, so they desert earlier in favour of pursuing other mating opportunities. However, one recent alternative hypothesis is that prolonged male parental care might also evolve if staying to care actively improves paternity. If this is the case, an increase in reproductive competition should be associated with increased paternal care. To test this prediction, we manipulated the level of reproductive competition experienced by burying beetles, Nicrophorus vespilloides (Herbst, 1783). We found that caregiving males stayed for longer and mated more frequently with their partner when reproductive competition was greater. Reproductive productivity did not increase when males extended care. Our findings provide support for the increased paternity hypothesis. Extended duration of parental care may be a male tactic both protecting investment (in the current brood) and maximizing paternity (in subsequent brood(s) via female stored sperm) even if this fails to maximize current reproductive productivity and creates conflict of interest with their mate via costs associated with increased mating frequency.
Abstract.
Author URL.
HOPWOOD PE, MOORE AJ, TREGENZA TOM, ROYLE NJ (2015). Niche variation and the maintenance of variation in body size in a burying beetle.
Ecological Entomology,
41(1), 96-104.
Abstract:
Niche variation and the maintenance of variation in body size in a burying beetle
1. In burying beetles (Nicrophorinae), body size is known to provide both a fecundity advantage (in females) and successful resource defence (in males and females). Despite this, considerable variation in body sizes is observed in natural populations.2. A possible explanation for the maintenance of this variation, even with intra‐ and inter‐specific resource competition, is that individuals might assort according to body size on different‐sized breeding resources.3. We tested prediction that ‘bigger is always better’, in the wild. and in the laboratory, by experimentally manipulating combinations of available breeding‐resource size (mouse carcasses) and competitor's body size in Nicrophorus vespilloides (Herbst 1783).4. In the field, large female beetles deserted small carcasses, without breeding, more often than they did larger carcasses, but small females used carcasses indiscriminately with respect to size. In the laboratory, large beetles reared larger broods (with more offspring) on larger carcasses than small beetles, but on small carcasses small beetles had a reproductive advantage over large ones. Offspring size covaried with carcass size independently of parental body size.5. The present combined results suggest breeding resource value depends on an individual's body size, and variation in body size is environmentally induced: maintained by differences in available carcass sizes. This produces a mechanism by which individual specialisation leads to an increase in niche variation via body size in these beetles.
Abstract.
2014
Pitchers W, Wolf JB, Tregenza T, Hunt J, Dworkin I (2014). Evolutionary rates for multivariate traits: the role of selection and genetic variation.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences,
369(1649).
Abstract:
Evolutionary rates for multivariate traits: the role of selection and genetic variation.
A fundamental question in evolutionary biology is the relative importance of selection and genetic architecture in determining evolutionary rates. Adaptive evolution can be described by the multivariate breeders' equation (Δz(-)=Gβ), which predicts evolutionary change for a suite of phenotypic traits (Δz(-)) as a product of directional selection acting on them (β) and the genetic variance-covariance matrix for those traits (G ). Despite being empirically challenging to estimate, there are enough published estimates of G and β to allow for synthesis of general patterns across species. We use published estimates to test the hypotheses that there are systematic differences in the rate of evolution among trait types, and that these differences are, in part, due to genetic architecture. We find some evidence that sexually selected traits exhibit faster rates of evolution compared with life-history or morphological traits. This difference does not appear to be related to stronger selection on sexually selected traits. Using numerous proposed approaches to quantifying the shape, size and structure of G, we examine how these parameters relate to one another, and how they vary among taxonomic and trait groupings. Despite considerable variation, they do not explain the observed differences in evolutionary rates.
Abstract.
Van Buskirk J, Krügel A, Kunz J, Miss F, Stamm A (2014). The Rate of Degradation of Chemical Cues Indicating Predation Risk: an Experiment and Review.
Ethology,
120(9), 942-949.
Abstract:
The Rate of Degradation of Chemical Cues Indicating Predation Risk: an Experiment and Review
AbstractMany prey taxa use kairomones or alarm pheromones to assess the risk of predation in aquatic environments, and the rate at which these cues attenuate determines how precisely they indicate the local density of predators. We estimated the rate of degradation of chemical cues generated by Aeshna dragonfly larvae feeding on Rana temporaria tadpoles. The half‐life of the cue was 35 h and was not influenced by whether it was aged in pond water or tap water or whether other tadpoles were present in the container in which cue‐aging occurred. A review of other published estimates of predator cue half‐life revealed values of 0.2–126 h, and variation among studies was unrelated to the type of aging water, the venue in which water was aged or prey behavior observed (laboratory, field), or the type of behavior that was recorded. We conclude that factors affecting the persistence of predator cues remain uncertain in spite of their importance for understanding the evolution of induced defenses.
Abstract.
Silk MJ, Croft DP, Tregenza T, Bearhop S (2014). The importance of fission-fusion social group dynamics in birds.
IBIS,
156(4), 701-715.
Author URL.
Pitchers WR, Klingenberg CP, Tregenza T, Hunt J, Dworkin I (2014). The potential influence of morphology on the evolutionary divergence of an acoustic signal.
J Evol Biol,
27(10), 2163-2176.
Abstract:
The potential influence of morphology on the evolutionary divergence of an acoustic signal.
The evolution of acoustic behaviour and that of the morphological traits mediating its production are often coupled. Lack of variation in the underlying morphology of signalling traits has the potential to constrain signal evolution. This relationship is particularly likely in field crickets, where males produce acoustic advertisement signals to attract females by stridulating with specialized structures on their forewings. In this study, we characterize the size and geometric shape of the forewings of males from six allopatric populations of the black field cricket (Teleogryllus commodus) known to have divergent advertisement calls. We sample from each of these populations using both wild-caught and common-garden-reared cohorts, allowing us to test for multivariate relationships between wing morphology and call structure. We show that the allometry of shape has diverged across populations. However, there was a surprisingly small amount of covariation between wing shape and call structure within populations. Given the importance of male size for sexual selection in crickets, the divergence we observe among populations has the potential to influence the evolution of advertisement calls in this species.
Abstract.
Author URL.
Neenan STV, Hodgson DJ, Tregenza T, Boothroyd D, Ellis CD (2014). The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus).
Aquaculture ResearchAbstract:
The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus)
Assessments of stock enhancement programmes for European lobsters (Homarus gammarus) require mark-recapture analysis of stocked individuals. However, established tag technology is deemed unsuitable for extensive use by many current lobster hatcheries, particularly upon the early juvenile stages. We tested the suitability of fluorescent Visible Implant Elastomer (VIE) tags for use in 5-month-old juvenile lobsters. Three treatment groups comprising 348 cultured lobsters in total were used to examine survival, growth and tag retention, and to assess mobility, shelter use and moulting behaviours. Tagging had no significant effect on lobster survival, growth, mobility, shelter use or moult frequency. Survival over 7 weeks was 75% among lobsters tagged with two elastomers, 76% in those with one elastomer and 74% among untagged controls. Mortality during moulting did not increase in tagged (6%) compared to untagged lobsters (9%). We found no evidence that VIE tags cause any negative effects that would be expected to inhibit survival upon wild release, but tag loss had reached 12% in both tagged treatments after 7 weeks and showed no sign of abating. Our study suggests that VIEs effectiveness in discerning cultured lobsters long after wild release may be limited when used in smaller juveniles. © 2014 John Wiley & Sons Ltd.
Abstract.
2013
Veen T, Faulks J, Tyler F, Lloyd J, Tregenza T (2013). Diverse reproductive barriers in hybridising crickets suggests extensive variation in the evolution and maintenance of isolation.
Evolutionary Ecology,
27(5), 993-1015.
Abstract:
Diverse reproductive barriers in hybridising crickets suggests extensive variation in the evolution and maintenance of isolation
Reproductive barriers reduce gene flow between populations and maintain species identities. A diversity of barriers exist, acting before, during and after mating. To understand speciation and coexistence, these barriers need to be quantified and their potential interactions revealed. We use the hybridising field crickets Gryllus bimaculatus and G. campestris as a model to understand the full compliment and relative strength of reproductive barriers. We find that males of both species prefer conspecific females, but the effect is probably too weak to represent a barrier. In contrast, prezygotic barriers caused by females being more attracted to conspecific male song and preferentially mounting and mating with conspecifics are strong and asymmetric. Postzygotic barriers vary in direction; reductions in fecundity and egg viability create selection against hybridisation, but hybrids live longer than pure-bred individuals. Hybrid females show a strong preference for G. bimaculatus songs, which together with a complete lack of hybridisation by G. campestris females, suggests that asymmetric gene flow is likely. For comparison, we review reproductive barriers that have been identified between other Gryllids and conclude that multiple barriers are common. Different species pairs are separated by qualitatively different combinations of barriers, suggesting that reproductive isolation and even the process of speciation itself may vary widely even within closely related groups. © 2012 Springer Science+Business Media Dordrecht.
Abstract.
Harrison XA, Hodgson DJ, Inger R, Colhoun K, Gudmundsson GA, McElwaine G, Tregenza T, Bearhop S (2013). Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
PLoS One,
8(10).
Abstract:
Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
In many animals, processes occurring in one season carry over to influence reproductive success and survival in future seasons. The strength of such carry-over effects is unlikely to be uniform across years, yet our understanding of the processes that are capable of modifying their strength remains limited. Here we show that female light-bellied Brent geese with higher body mass prior to spring migration successfully reared more offspring during breeding, but only in years where environmental conditions during breeding were favourable. In years of bad weather during breeding, all birds suffered reduced reproductive output irrespective of pre-migration mass. Our results suggest that the magnitude of reproductive benefits gained by maximising body stores to fuel breeding fluctuates markedly among years in concert with conditions during the breeding season, as does the degree to which carry-over effects are capable of driving variance in reproductive success among individuals. Therefore while carry-over effects have considerable power to drive fitness asymmetries among individuals, our ability to interpret these effects in terms of their implications for population dynamics is dependent on knowledge of fitness determinants occurring in subsequent seasons.
Abstract.
Author URL.
Tyler F, Rodríguez-Muñoz R, Tregenza T (2013). Fertilisation and early developmental barriers to hybridisation in field crickets.
BMC Evol Biol,
13Abstract:
Fertilisation and early developmental barriers to hybridisation in field crickets.
BACKGROUND: Post-mating interactions between the reproductive traits and gametes of mating individuals and among their genes within zygotes are invariably complex, providing multiple opportunities for reproduction to go awry. These interactions have the potential to act as barriers to gene flow between species, and may be important in the process of speciation. There are multiple post-mating barriers to interbreeding between the hybridising field crickets Gryllus bimaculatus and G. campestris. Female G. bimaculatus preferentially store sperm from conspecific males when mated to both conspecific and heterospecific partners. Additionally, conspecific males sire an even greater proportion of offspring than would be predicted from their sperm's representation in the spermatheca. The nature of these post-sperm-storage barriers to hybridisation are unknown. We use a fluorescent staining technique to determine whether barriers occur prior to, or during embryo development. RESULTS: We show that eggs laid by G. bimaculatus females mated to G. campestris males are less likely to begin embryogenesis than eggs from conspecific mating pairs. of the eggs that are successfully fertilised and start to develop, those from heterospecific mating pairs are more likely to arrest early, prior to blastoderm formation. We find evidence for bimodal variation among egg clutches in the number of developing embryos that subsequently arrest, indicating that there is genetic variation for incompatibility between mating individuals. In contrast to the pattern of early embryonic mortality, those hybrids reaching advanced stages of embryogenesis have survival rates equal to that of embryos from conspecific mating pairs. CONCLUSIONS: Post-sperm-storage barriers to hybridisation show evidence of genetic polymorphism. They are sufficiently large, that if the species interbreed where they are sympatric, these barriers could play a role in the maintenance of reproductive isolation between them. The number of eggs that fail to develop represents a substantial cost of hybridization to G. bimaculatus females, and this cost could reinforce the evolution of barriers occurring earlier in the reproductive process.
Abstract.
Author URL.
Pitchers WR, Brooks R, Jennions MD, Tregenza T, Dworkin I, Hunt J (2013). Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
Journal of Evolutionary Biology,
26(5), 1060-1078.
Abstract:
Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus
Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders' equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance-covariance matrix (P) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild-caught crickets from each of the populations and then a second subset after rearing crickets under common-garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high- and low-nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit. © 2013 the Authors. © 2013 European Society for Evolutionary Biology.
Abstract.
Brooks R, Pitchers WR, Jennions MD, Tregenza T, Dworkin I, Hunt J (2013). Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
J Evol Biol,
26(5), 1060-1078.
Abstract:
Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders' equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance-covariance matrix (P) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild-caught crickets from each of the populations and then a second subset after rearing crickets under common-garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high- and low-nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit.
Abstract.
Author URL.
Tyler F, Harrison XA, Bretman A, Veen T, Rodríguez-Muñoz R, Tregenza T (2013). Multiple post-mating barriers to hybridization in field crickets.
Molecular Ecology,
22(6), 1640-1649.
Abstract:
Multiple post-mating barriers to hybridization in field crickets
Mechanisms that prevent different species from interbreeding are fundamental to the maintenance of biodiversity. Barriers to interspecific matings, such as failure to recognize a potential mate, are often relatively easy to identify. Those occurring after mating, such as differences in the how successful sperm are in competition for fertilisations, are cryptic and have the potential to create selection on females to mate multiply as a defence against maladaptive hybridization. Cryptic advantages to conspecific sperm may be very widespread and have been identified based on the observations of higher paternity of conspecifics in several species. However, a relationship between the fate of sperm from two species within the female and paternity has never been demonstrated. We use competitive microsatellite PCR to show that in two hybridising cricket species, Gryllus bimaculatus and G. campestris, sequential cryptic reproductive barriers are present. In competition with heterospecifics, more sperm from conspecific males is stored by females. Additionally, sperm from conspecific males has a higher fertilisation probability. This reveals that conspecific sperm precedence can occur through processes fundamentally under the control of females, providing avenues for females to evolve multiple mating as a defence against hybridization, with the counterintuitive outcome that promiscuity reinforces isolation and may promote speciation. © 2013 Blackwell Publishing Ltd.
Abstract.
Tyler F, Harrison XA, Bretman A, Veen T, Rodríguez-Muñoz R, Tregenza T (2013). Multiple post-mating barriers to hybridization in field crickets.
Mol Ecol,
22(6), 1640-1649.
Abstract:
Multiple post-mating barriers to hybridization in field crickets.
Mechanisms that prevent different species from interbreeding are fundamental to the maintenance of biodiversity. Barriers to interspecific matings, such as failure to recognize a potential mate, are often relatively easy to identify. Those occurring after mating, such as differences in the how successful sperm are in competition for fertilisations, are cryptic and have the potential to create selection on females to mate multiply as a defence against maladaptive hybridization. Cryptic advantages to conspecific sperm may be very widespread and have been identified based on the observations of higher paternity of conspecifics in several species. However, a relationship between the fate of sperm from two species within the female and paternity has never been demonstrated. We use competitive microsatellite PCR to show that in two hybridising cricket species, Gryllus bimaculatus and G. campestris, sequential cryptic reproductive barriers are present. In competition with heterospecifics, more sperm from conspecific males is stored by females. Additionally, sperm from conspecific males has a higher fertilisation probability. This reveals that conspecific sperm precedence can occur through processes fundamentally under the control of females, providing avenues for females to evolve multiple mating as a defence against hybridization, with the counterintuitive outcome that promiscuity reinforces isolation and may promote speciation.
Abstract.
Author URL.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2013). No benefits of polyandry to female green turtles.
Behavioral Ecology,
24(4), 1022-1029.
Abstract:
No benefits of polyandry to female green turtles
Multiple paternity is extremely common in natural populations of almost all reptiles studied to date, suggesting that pay-offs from polyandrous mating systems are important in these taxonomic groups. However, strong evidence in support of direct or indirect benefits to females is scarce. We examined the relationship between polyandry and components of female reproductive success and offspring fitness in the promiscuous green turtle (Chelonia mydas), a species that exhibits highly variable levels of multiple paternity. We did not detect any clear fitness benefits to polyandrous females in this study, and we discuss the potential of sexual conflict to influence female mating patterns in marine turtles. We show that polyandrous females produce significantly smaller clutches than monandrous females, highlighting a potential cost to polyandry in green turtles. Furthermore, multiple paternity was more common in returning females (recorded breeding in a previous season) than in females nesting for the first time at our study site, possibly reflecting increased encounter rates with males or sperm storage across breeding seasons. Our results reveal potentially complex influences of female traits, environment, and mating strategy on components of reproductive success, and we discuss the challenges associated with unraveling the costs and benefits of multiple mating in natural populations. © 2013 the Author. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.
Abstract.
Attisano A, Tregenza T, Moore AJ, Moore PJ (2013). Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciatus. Animal Behaviour
Attisano A, Tregenza T, Moore AJ, Moore PJ (2013). Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciatus.
Animal Behaviour,
86(3), 651-657.
Abstract:
Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciatus
Migration evolves as a response to seasonally unfavourable environments but plasticity in reproductive physiology is another avenue by which insects can respond to resource-poor conditions. We investigated the relationship between individual variation in migratory propensity and the level of response to poor conditions modulated by the female reproductive physiology. We tested the hypothesis that, compared to migrants, residential behaviour is associated with a higher degree of phenotypic plasticity in oosorption, an adaptive physiological mechanism that allows females to recoup resources from undeveloped oocytes. Reallocation from reproduction to survival would allow females to skip migration and to cope with unfavourable environments. If this plasticity is evolved, we further predicted it would vary between as well as within populations. We examined variation associated with migratory behaviour in females from four populations of the milkweed bug, Oncopeltus fasciatus, using a behavioural assay to categorize females as either migrant or resident and observing the differences in oosorption between these groups. As expected, food availability, source population and wing length influenced the propensity for migratory flight, and food availability influenced levels of oosorption. We also found support for our key prediction that resident females are characterized by higher levels of ovarian oosorption than migrant females. Our study provides support for a physiological difference between migrant and resident females and suggests the presence of both physiological and behavioural tactics that interact with the potential for migration to provide adaptation to seasonally challenging environments. © 2013 the Association for the Study of Animal Behaviour.
Abstract.
Pincheira-Donoso D, Tregenza T, Witt MJ, Hodgson DJ (2013). The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac. Global Ecology and Biogeography
Pincheira-Donoso D, Tregenza T, Witt MJ, Hodgson DJ (2013). The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac.
Global Ecology and Biogeography,
22(7), 857-867.
Abstract:
The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac
Aim: Evolutionary radiations into novel areas or niches require innovative adaptations. However, rapid subsequent changes in these novel conditions might demand rapid re-adaptations to secure population persistence and prevent extinction. We propose that reptilian viviparity (live birth) is consistent with such a scenario. Using the Liolaemus lizard radiation, we investigate the hypotheses that historical invasions of cold climates have been permitted by transitions to viviparity, and that this parity mode is irreversible. Then, we investigate whether these combined factors restrict viviparous lizards to cold climates, and hence, whether viviparous species are particularly threatened by climate change. Location: South America. Methods: We employ phylogenetic analyses to investigate evolutionary transitions in reproductive modes and their consequences for environmental restrictions in viviparous lizards. We then employ climatic projections to predict the impact of climate change on the future persistence of these organisms. Results: the oviparity-to-viviparity transition is consistently associated with colonization of cold climates, and appears to be irreversible. Since viviparity seems less viable (compared with oviparity) in warm climates, species that evolve viviparity in cold climates are likely to remain adaptively constrained to such environments. Therefore, upward-poleward advances of climate warming will cause severe shifts and contractions of viviparous species ranges, threatening major extinctions over the next half century. Main conclusions: Viviparity has been largely responsible for the successful radiation of Liolaemus into cold climates, but since this adaptation is predominantly viable in these environments and is unlikely to re-evolve into oviparity, viviparity may prove to be an evolutionary dead-end for lizards facing rapid climate change. © 2013 John Wiley & Sons Ltd.
Abstract.
Christmas JT, Everson RM, Rodriguez-Munoz R, Tregenza T (2013). Variational Bayesian Tracking: Whole Track Convergence for Large Scale Ecological Video Monitoring. IEEE International Joint Conference on Neural Networks (IJCNN). 5th - 9th Aug 2013.
Christmas J, Everson R, Rodriguez-Munoz R, Tregenza T (2013). Variational Bayesian Tracking: Whole Track Convergence for Large-scale Ecological Video Monitoring.
Author URL.
Tyler F, Tregenza T (2013). Why do so many flour beetle copulations fail?.
Entomologia Experimentalis et Applicata,
146(1), 199-206.
Abstract:
Why do so many flour beetle copulations fail?
Copulations that fail to result in fertilisations are common across a broad range of species, and remain enigmatic given the inherent costs that are being paid by both partners. The determinants of failures are varied and can take effect before, during, or after copulating. In the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), population estimates of copulations failing to result in fertilisations as high as 55% have been reported, suggesting that the causes of these failures play an important role in the mating system, or that the costs experienced by those determining failure, in this system likely the females, is low. Here, we show that failure is determined peri-copulation; successful spermatophore transfer (indicated by change in mass of mating individuals) typically results in offspring production, suggesting that mechanisms of post-copulatory female choice do not cause outright failure. The proportion of copulations that failed to result in fertilisations was apparently not influenced by the relatedness of mating pairs, the age, mating status, or mass of the female, or the interval she experienced between matings. This suggests that alternative adaptive explanations are responsible for the prevalence of copulations that fail to result in fertilisations in this species, or that the costs involved are sufficiently small, so that selection against such failures is weak. © 2012 the Authors Entomologia Experimentalis et Applicata © 2012 the Netherlands Entomological Society.
Abstract.
2012
Veen T, Faulks J, Tyler F, Lloyd J, Tregenza T (2012). Diverse reproductive barriers in hybridising crickets suggests extensive variation in the evolution and maintenance of isolation. Evolutionary Ecology, 1-23.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2012). Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
Molecular Ecology,
21(14), 3625-3635.
Abstract:
Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1 year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult. © 2012 Blackwell Publishing Ltd.
Abstract.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2012). Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
Mol Ecol,
21(14), 3625-3635.
Abstract:
Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult.
Abstract.
Author URL.
Sharma MD, Griffin RM, Hollis J, Tregenza T, Hosken DJ (2012). Reinvestigating good genes benefits of mate choice in Drosophila simulans.
Biological Journal of the Linnean Society,
106(2), 295-306.
Abstract:
Reinvestigating good genes benefits of mate choice in Drosophila simulans
Studies investigating the genetic benefits of female mate choice frequently find Fisherian benefits to choice, at the same time as detecting small or no good genes (viability) effects. This could be because sons trade-off viability for increased mating success and, accordingly, it has been suggested that good genes benefits should be investigated in daughters. However, good genes benefits via daughters could also be disrupted by intralocus sexual conflict. As a result, it is not clear when and if good genes benefits should accrue. We investigated potential good genes effects in Drosophila simulans using an isofemale line approach. We assessed the attractiveness of males in two different ways and then measured the longevity, as well as lifetime reproductive success, of their daughters. We also assessed potential direct benefits of female mate choice and good genes effects through the longevity of sons. We found no evidence of direct or good genes benefits to females mating with attractive males, and the failure to find good genes effects via daughters was apparently not a result of masking through intralocus sexual conflict. The results obtained in the present study are consistent with previous findings in this species, and suggest that good genes benefits are at best very small in our study population. © 2012 the Linnean Society of London.
Abstract.
Sharma MD, Mitchell C, Hunt J, Tregenza T, Hosken DJ (2012). The genetics of cuticular hydrocarbon profiles in the Fruit Fly Drosophila simulans.
J Hered,
103(2), 230-239.
Abstract:
The genetics of cuticular hydrocarbon profiles in the Fruit Fly Drosophila simulans.
Female mate choice is one mechanism of sexual selection and, provided there is adequate genetic variation in the male traits that are the target of this selection, they will evolve via female choice. Cuticular hydrocarbons (CHCs) are important in Drosophila mate choice, but relatively little is known about the underlying genetic architecture of CHC profiles in Drosophila simulans. Here, we used gas chromatography-mass spectrometry to investigate patterns of genetic variation in the CHC profiles of male and female D. simulans using isofemale lines. We found substantial genetic variation for CHC profiles and individual CHC components, and individual CHCs were frequently strongly genetically correlated, with a tendency for negative covariance between long- and short-chain CHCs in males. Intersexual genetic covariances were often weak and frequently differed in sign. These findings are novel and significant, highlighting the previously unexplored genetic architecture of CHCs in D. simulans and suggest that this architecture may facilitate sex-specific CHC evolution.
Abstract.
Author URL.
Wright LI, Stokes KL, Fuller WJ, Godley BJ, McGowan A, Snape R, Tregenza T, Broderick AC (2012). Turtle mating patterns buffer against disruptive effects of climate change.
Proc Biol Sci,
279(1736), 2122-2127.
Abstract:
Turtle mating patterns buffer against disruptive effects of climate change.
For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2-4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.
Abstract.
Author URL.
Tyler F, Tregenza T (2012). Why do so many flour beetle copulations fail. Entomologia Experimentalis et Applicata
2011
Pincheira-Donoso D, Tregenza T (2011). Fecundity Selection and the Evolution of Reproductive Output and Sex-Specific Body Size in the Liolaemus Lizard Adaptive Radiation.
Evolutionary Biology,
38(2), 197-207.
Abstract:
Fecundity Selection and the Evolution of Reproductive Output and Sex-Specific Body Size in the Liolaemus Lizard Adaptive Radiation
Fecundity is a primary component of fitness. Theory predicts that the evolution of fecundity through increased brood size results from fecundity selection favouring larger female size to accommodate more offspring and to store more energy. This is expected to generate asymmetric selection on body size between the sexes, ultimately driving evolution of female-biased sexual size dimorphism. Additionally, it has been predicted that the intensity of fecundity selection increases when the opportunities for reproduction are reduced by the limiting thermal effects of increasing latitude-elevation (i.e. decreasing environmental temperatures) on the length of the reproductive season. This later factor would be particularly strong among ectotherms, where reproduction is heavily temperature-dependent. However, this integrative perspective on reproductive evolution by fecundity selection has rarely been investigated. Here, we employ a comparative approach to investigate these predictions in Liolaemus, a prominent lizard radiation. As expected, Liolaemus reproductive output (i. e. offspring number per reproductive episode) increases predictably with increasing female size. However, contrary to predictions, we found that increased fecundity does not translate into female-biased SSD, and that combined latitude-elevation does not impose a detectable effect on fecundity. Finally, our allometric analyses reveal that SSD scales with body size, which supports the occurrence of Rensch's rule in these lizards. We discuss the evolutionary implications of our results, and the assumptions of the investigated hypotheses. © 2011 Springer Science+Business Media, LLC.
Abstract.
Bretman A, Rodríguez-Muñoz R, Walling C, Slate J, Tregenza T (2011). Fine-scale population structure, inbreeding risk and avoidance in a wild insect population.
Mol Ecol,
20(14), 3045-3055.
Abstract:
Fine-scale population structure, inbreeding risk and avoidance in a wild insect population.
The ecological and evolutionary importance of fine-scale genetic structure within populations is increasingly appreciated. However, available data are largely restricted to wild vertebrates and eusocial insects. In addition, there is the expectation that most insects tend to have such large- and high-density populations and are so mobile that they are unlikely to face inbreeding risks through fine-scale population structuring. This has made the growing body of evidence for inbreeding avoidance in insects and its implication in mating systems evolution somewhat enigmatic. We present a 4-year study of a natural population of field crickets. Using detailed video monitoring combined with genotyping, we track the movement of all adults within the population and investigate genetic structure at a fine scale. We find some evidence for relatives being found in closer proximity, both across generations and within a single breeding season. Whilst incestuous matings are not avoided, population inbreeding is low, suggesting that mating is close to random and the limited fine-scale structure does not create significant inbreeding risk. Hence, there is little evidence for selective pressures associated with the evolution of inbreeding avoidance mechanisms in a closely related species.
Abstract.
Author URL.
Rodríguez-Muñoz R, Bretman A, Tregenza T (2011). Guarding males protect females from predation in a wild insect.
Curr Biol,
21(20), 1716-1719.
Abstract:
Guarding males protect females from predation in a wild insect.
Males frequently remain in close proximity to their mate immediately postcopulation. This behavior has generally been interpreted as a guarding tactic designed to reduce the likelihood that a rival male can rapidly displace the ejaculate of the guarding male [1, 2]. Such attempts by males to control their mates represent a potential source of conflict [3-5], but guarding behaviors in species where it is difficult for males to control their mates suggest that conflict is not inevitable [6, 7]. We employed a network of infrared video cameras to study a wild population of individually marked and genotyped field crickets (Gryllus campestris). Lone females or males suffer similar rates of predation, but when a pair is attacked, the male allows the female priority access to their burrow, and in doing so dramatically increases his probability of being killed. In compensation for this increased predation risk, paired males mate more frequently and father more of the female's offspring. By staying with a male, females increase the sperm contribution of preferred males as well as reducing their predation risk. In contrast to conclusions based on previous lab studies, our field study suggests that mate guarding can evolve in a context of cooperation rather than conflict between the sexes.
Abstract.
Author URL.
HARRISON XA, BEARHOP S, INGER R, COLHOUN K, GUDMUNDSSON GA, HODGSON D, McELWAINE GRAHAM, TREGENZA TOM (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects. Molecular Ecology, 20(22), 4786-4795.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson D, McElwaine G, Tregenza T (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Molecular ecology,
20(22), 4786-4795.
Abstract:
Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Studies in a multitude of taxa have described a correlation between heterozygosity and fitness and usually conclude that this is evidence for inbreeding depression. Here, we have used multilocus heterozygosity (MLH) estimates from 15 microsatellite markers to show evidence of heterozygosity-fitness correlations (HFCs) in a long-distance migratory bird, the light-bellied Brent goose. We found significant, positive heterozygosity-heterozygosity correlations between random subsets of the markers we employed, and no evidence that a model containing all loci as individual predictors in a multiple regression explained significantly more variation than a model with MLH as a single predictor. Collectively, these results lend support to the hypothesis that the HFCs we have observed are a function of inbreeding depression. However, we do find that fitness correlations are only detectable in years where population-level productivity is high enough for the reproductive asymmetry between high and low heterozygosity individuals to become apparent. We suggest that lack of evidence of heterozygosity-fitness correlations in animal systems may be because heterozygosity is a poor proxy measure of inbreeding, especially when employing low numbers of markers, but alternatively because the asymmetries between individuals of different heterozygosities may only be apparent when environmental effects on fitness are less pronounced. © 2011 Blackwell Publishing Ltd.
Abstract.
Sinclair BJ, Bretman A, Tregenza T, Tomkins JL, Hosken DJ (2011). Metabolic rate does not decrease with starvation in Gryllus bimaculatus when changing fuel use is taken into account.
Physiological Entomology,
36(1), 84-89.
Abstract:
Metabolic rate does not decrease with starvation in Gryllus bimaculatus when changing fuel use is taken into account
Many behavioural traits are considered to be condition-dependent, reflecting the differential allocation of resources to fitness-related traits and maintenance, although the physiological underpinnings of condition dependence are not well understood. In the present study, the hypothesis that condition dependence in male Gryllus bimaculatus De Geer is mediated by a decrease in metabolic rate with declining condition is tested. CO2 production is measured by flow-through respirometry, with insect condition manipulated through starvation. Crickets starved for 7 days have lower CO2 emission rates than individuals starved for only 24 h. However, carbohydrate reserves are depleted in the first 3 days, suggesting that the initial metabolism is primarily fuelled by carbohydrate, with a shift to lipid stores after 3 days. If the metabolic rate is estimated using respiratory quotients reflecting this shift in fuels, there is no difference in metabolic rate between crickets starved for 24 h and 7 days, suggesting that metabolic rate does not decrease with declining condition. This implies that a decrease in metabolic rate during starvation may not be a general pattern in insects, and emphasizes the need to consider fuel use during metabolic rate estimation in starvation studies. © 2010 the Authors. Physiological Entomology © 2010 the Royal Entomological Society.
Abstract.
Veen T, Faulks J, Rodríguez-Muñoz R, Tregenza T (2011). Premating reproductive barriers between hybridising cricket species differing in their degree of polyandry.
PLoS One,
6(5).
Abstract:
Premating reproductive barriers between hybridising cricket species differing in their degree of polyandry.
Understanding speciation hinges on understanding how reproductive barriers arise between incompletely isolated populations. Despite their crucial role in speciation, prezygotic barriers are relatively poorly understood and hard to predict. We use two closely related cricket species, Gryllus bimaculatus and G. campestris, to experimentally investigate premating barriers during three sequential mate choice steps. Furthermore, we experimentally show a significant difference in polyandry levels between the two species and subsequently test the hypothesis that females of the more polyandrous species, G. bimaculatus, will be less discriminating against heterospecific males and hence hybridise more readily. During close-range mating behaviour experiments, males showed relatively weak species discrimination but females discriminated very strongly. In line with our predictions, this discrimination is asymmetric, with the more polyandrous G. bimaculatus mating heterospecifically and G. campestris females never mating heterospecifically. Our study shows clear differences in the strength of reproductive isolation during the mate choice process depending on sex and species, which may have important consequences for the evolution of reproductive barriers.
Abstract.
Author URL.
Sharma MD, Tregenza T, Hosken DJ (2011). Sex combs, allometry, and asymmetry in Drosophila.
Biological Journal of the Linnean Society,
103(4), 923-934.
Abstract:
Sex combs, allometry, and asymmetry in Drosophila
There has been recent debate about the expected allometry of sexually-selected traits. Although sexually-selected traits exhibit a diversity of allometric patterns, signalling characters are frequently positively allometric. By contrast, insect genitalia tend to be negatively allometric, although the allometry of nongenital sexually-selected characters in insects is largely unknown (with some notable exceptions). It has also been suggested that there should be a negative association between the asymmetry and size of bilaterally-paired, sexually-selected traits, although this claim is controversial. We assessed the allometry and asymmetry (fluctuating asymmetry, FA) of a nongenital contact-courtship structure, the sex comb, in replicate populations of three species of Drosophila (we also measured wing FA). Sex combs are sexually-selected characters used to grasp the female's abdomen and genitalia and to spread her wings prior to and during copulation. Although species differed in the size of the sex combs, all combs were positively allometric, and comb allometry did not generally differ significantly between species or populations. Comb and wing asymmetry did vary across species, although not across populations of the same species. However, FA was trait specific and was never negatively associated with trait size. © 2011 the Linnean Society of London.
Abstract.
Gay L, Hosken DJ, Eady P, Vasudev R, Tregenza T (2011). The evolution of harm--effect of sexual conflicts and population size.
Evolution,
65(3), 725-737.
Abstract:
The evolution of harm--effect of sexual conflicts and population size.
Conflicts of interest between mates can promote the evolution of male traits that reduce female fitness and that drive coevolution between the sexes. The rate of adaptation depends on the intensity of selection and its efficiency, which depends on drift and genetic variability. This leads to the largely untested prediction that coevolutionary adaptations such as those driven by sexual conflict should evolve faster in large populations. We tested this using the bruchid beetle Callosobruchus maculatus, a species where harm inflicted by males is well documented. Although most experimental evolution studies remove sexual conflict, we reintroduced it in populations in which it had been experimentally removed. Both population size and standing genetic variability were manipulated in a factorial experimental design. After 90 generations of relaxed conflict (monogamy), the reintroduction of sexual conflicts for 30 generations favored males that harmed females and females that were more resistant to the genital damage inflicted by males. Males evolved to become more harmful when population size was large rather than when initial genetic variation was enriched. Our study shows that sexual selection can create conditions in which males can benefit from harming females and that selection may tend to be more intense and effective in larger populations.
Abstract.
Author URL.
Gay L, Brown E, Tregenza T, Pincheira-Donoso D, Eady PE, Vasudev R, Hunt J, Hosken DJ (2011). The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus.
J Evol Biol,
24(2), 449-456.
Abstract:
The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus.
Males harm females during mating in a range of species. This harm is thought to evolve because it is directly or indirectly beneficial to the male, despite being costly to his mate. The resulting sexually antagonistic selection can cause sexual arms races. For sexually antagonistic co-evolution to occur, there must be genetic variation for traits involved in female harming and susceptibility to harm, but even then intersexual genetic correlations could facilitate or impede sexual co-evolution. Male Callosobruchus maculatus harm their mates during copulation by damaging the female's reproductive tract. However, there have been no investigations of the genetic variation in damage or in female susceptibility to damage, nor has the genetic covariance between these characters been assessed. Here, we use a full-sib/half-sib breeding design to show that male damage is heritable, whereas female susceptibility to damage is much less so. There is also a substantial positive genetic correlation between the two, suggesting that selection favouring damaging males will increase the prevalence of susceptible females. We also provide evidence consistent with intralocus sexual conflict in this species.
Abstract.
Author URL.
Lewis Z, Champion de Crespigny FE, Sait SM, Tregenza T, Wedell N (2011). Wolbachia infection lowers fertile sperm transfer in a moth.
Biol Lett,
7(2), 187-189.
Abstract:
Wolbachia infection lowers fertile sperm transfer in a moth.
The endosymbiotic bacterium Wolbachia pipientis manipulates host reproduction by rendering infected males reproductively incompatible with uninfected females (cytoplasmic incompatibility; CI). CI is believed to occur as a result of Wolbachia-induced modifications to sperm during maturation, which prevent infected sperm from initiating successful zygote development when fertilizing uninfected females' eggs. However, the mechanism by which CI occurs has been little studied outside the genus Drosophila. Here, we show that in the sperm heteromorphic Mediterranean flour moth, Ephestia kuehniella, infected males transfer fewer fertile sperm at mating than uninfected males. In contrast, non-fertile apyrene sperm are not affected. This indicates that Wolbachia may only affect fertile sperm production and highlights the potential of the Lepidoptera as a model for examining the mechanism by which Wolbachia induces CI in insects.
Abstract.
Author URL.
2010
Harrison XA, Tregenza T, Inger R, Colhoun K, Dawson DA, Gudmundsson GA, Hodgson DJ, Horsburgh GJ, McElwaine G, Bearhop S, et al (2010). Cultural Inheritance Drives Site Fidelity and Migratory Connectivity in a Long Distance Migrant. Molecular Ecology, 19(24), 5484-5496.
Brown EA, Gay L, Vasudev R, Tregenza T, Eady PE, Hosken DJ (2010). Erratum: Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles (Heredity (2010) 105 (576) DOI:10.1038/hdy.2010.132). Heredity, 105(6).
Sharma MD, Tregenza T, Hosken DJ (2010). Female mate preferences in Drosophila simulans: evolution and costs.
J Evol Biol,
23(8), 1672-1679.
Abstract:
Female mate preferences in Drosophila simulans: evolution and costs.
Female mate preference is central to sexual selection, and all indirect benefit models require that there is genetic variation in female preference. This has rarely been tested however, with relatively few studies documenting heritable variation in female preference and even fewer that have directly selected on mate preference to unequivocally show that it can evolve. Additionally, costs of mate preference are poorly understood even though these have implications for preference evolution. We selected on female preference for ebony-males in replicate Drosophila simulans lines, and generated a rapid evolutionary response in both replicates, with the proportion of females mating with ebony-males increasing from approximately 5% to 30% after five generations of selection. This increase was independent of changes in ebony-males as only females were included in our selection regime. We could detect no cost to mate preference itself other than that associated with the fitness consequences of mating with ebony males.
Abstract.
Author URL.
Arnqvist G, Dowling DK, Eady P, Gay L, Tregenza T, Tuda M, Hosken DJ (2010). Genetic architecture of metabolic rate: environment specific epistasis between mitochondrial and nuclear genes in an insect.
Evolution,
64(12), 3354-3363.
Abstract:
Genetic architecture of metabolic rate: environment specific epistasis between mitochondrial and nuclear genes in an insect.
The extent to which mitochondrial DNA (mtDNA) variation is involved in adaptive evolutionary change is currently being reevaluated. In particular, emerging evidence suggests that mtDNA genes coevolve with the nuclear genes with which they interact to form the energy producing enzyme complexes in the mitochondria. This suggests that intergenomic epistasis between mitochondrial and nuclear genes may affect whole-organism metabolic phenotypes. Here, we use crossed combinations of mitochondrial and nuclear lineages of the seed beetle Callosobruchus maculatus and assay metabolic rate under two different temperature regimes. Metabolic rate was affected by an interaction between the mitochondrial and nuclear lineages and the temperature regime. Sequence data suggests that mitochondrial genetic variation has a role in determining the outcome of this interaction. Our genetic dissection of metabolic rate reveals a high level of complexity, encompassing genetic interactions over two genomes, and genotype × genotype × environment interactions. The evolutionary implications of these results are twofold. First, because metabolic rate is at the root of life histories, our results provide insights into the complexity of life-history evolution in general, and thermal adaptation in particular. Second, our results suggest a mechanism that could contribute to the maintenance of nonneutral mtDNA polymorphism.
Abstract.
Author URL.
Holwell GI, Winnick C, Tregenza T, Herberstein ME (2010). Genital shape correlates with sperm transfer success in the praying mantis Ciulfina klassi (Insecta: Mantodea).
Behavioral Ecology and Sociobiology,
64(4), 617-625.
Abstract:
Genital shape correlates with sperm transfer success in the praying mantis Ciulfina klassi (Insecta: Mantodea)
The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated. Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly, two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success. Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer. © 2009 Springer-Verlag.
Abstract.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T, Bearhop S (2010). Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources, 2, 365-371.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T, Bearhop S (2010). Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources, 1-7.
Rodríguez-Muñoz R, Bretman A, Slate J, Walling CA, Tregenza T (2010). Natural and sexual selection in a wild insect population.
Science,
328(5983), 1269-1272.
Abstract:
Natural and sexual selection in a wild insect population.
The understanding of natural and sexual selection requires both field and laboratory studies to exploit the advantages and avoid the disadvantages of each approach. However, studies have tended to be polarized among the types of organisms studied, with vertebrates studied in the field and invertebrates in the lab. We used video monitoring combined with DNA profiling of all of the members of a wild population of field crickets across two generations to capture the factors predicting the reproductive success of males and females. The factors that predict a male's success in gaining mates differ from those that predict how many offspring he has. We confirm the fundamental prediction that males vary more in their reproductive success than females, and we find that females as well as males leave more offspring when they mate with more partners.
Abstract.
Author URL.
Schuett W, Tregenza T, Dall SRX (2010). Sexual selection and animal personality.
Biol Rev Camb Philos Soc,
85(2), 217-246.
Abstract:
Sexual selection and animal personality.
Consistent individual behavioural tendencies, termed "personalities", have been identified in a wide range of animals. Functional explanations for personality have been proposed, but as yet, very little consideration has been given to a possible role for sexual selection in maintaining differences in personality and its stability within individuals. We provide an overview of the available literature on the role of personality traits in intrasexual competition and mate choice in both human and non-human animals and integrate this into a framework for considering how sexual selection can generate and maintain personality. For this, we consider the evolution and maintenance of both main aspects of animal personality: inter-individual variation and intra-individual consistency.
Abstract.
Author URL.
2009
Pincheira-Donoso D, Hodgson DJ, Stipala J, Tregenza T (2009). A phylogenetic analysis of sex-specific evolution of ecological morphology in Liolaemus lizards.
Ecological Research,
24(6), 1223-1231.
Abstract:
A phylogenetic analysis of sex-specific evolution of ecological morphology in Liolaemus lizards
Adaptive radiation theory predicts that phenotypic traits involved in ecological performance evolve in different directions in populations subjected to divergent natural selection, resulting in the evolution of ecological diversity. This idea has largely been supported through comparative studies exploring relationships between ecological preferences and quantitative traits among different species. However, intersexual perspectives are often ignored. Indeed, although it is well established that intersexual competition and sex-specific parental and reproductive roles may often subject sex-linked phenotypes to antagonistic selection effects, most ecomorphological research has explored adaptive evolution on a single sex, or on means obtained from both sexes together. The few studies taking sexual differences into account reveal the occurrence of sex-specific ecomorphs in some clades of lizards, and conclude that the independent contribution of the sexes to the morphological diversity produced by adaptive radiation can be substantial. Here, we investigate whether microhabitat use results in the evolution of sex-specific ecomorphs across 44 Liolaemus lizard species. We found that microhabitat structure does not predict variation in body size and shape in either of the sexes. Yet, we found that males and females tend to occupy significantly different positions in multivariate morphological spaces, indicating that treating males and females as ecologically and phenotypically equivalent units may lead to incomplete or mistaken estimations of the diversity produced by adaptive evolution. © the Ecological Society of Japan 2009.
Abstract.
Davies TE, Beanjara N, Tregenza T (2009). A socio-economic perspective on gear-based management in an artisanal fishery in south-west Madagascar.
Fisheries Management and Ecology,
16(4), 279-289.
Abstract:
A socio-economic perspective on gear-based management in an artisanal fishery in south-west Madagascar
Artisanal fisheries are important socially, nutritionally and economically. Poverty is common in communities dependent on such fisheries, making sustainable management difficult. Poverty based on material style of life (MSL) was assessed, livelihoods surveyed and the relationship between these factors and fishery data collected using a fish landing study were examined. Species richness, diversity, size and mean trophic level of catches were determined for six fishing gears in an artisanal fishery in south-west Madagascar. There was little livelihood diversification and respondents were highly dependent on the fishery. No relationship was found between poverty and gear use. This suggests that poverty does not have a major impact on the nature of the fishery; however, this study was dominated by poor households, so it remains possible that communities with more variation in wealth might show differences in fishing methods according to this parameter. The fishery was heavily exploited with a predominance of small fish in the catches. Beach seines caught some of the smallest fish, overlapped in selectivity with gill nets and also had the highest catch per fishers. Thus, a reduction in the number of beach seines could help reduce the catch of small fish and the overlap in selectivity among gears. © 2009 Blackwell Publishing Ltd.
Abstract.
Gay L, Eady PE, Vasudev R, Hosken DJ, Tregenza T (2009). Costly sexual harassment in a beetle.
Physiological Entomology,
34(1), 86-92.
Abstract:
Costly sexual harassment in a beetle
The optimal number of mating partners for females rarely coincides with that for males, leading to sexual conflict over mating frequency. In the bruchid beetle Callosobruchus maculatus, the fitness consequences to females of engaging in multiple copulations are complex, with studies demonstrating both costs and benefits to multiple mating. However, females kept continuously with males have a lower lifetime egg production compared with females mated only once and then isolated from males. This reduction in fitness may be a result of damage caused by male genitalia, which bear spines that puncture the female's reproductive tract, and/or toxic elements in the ejaculate. However, male harassment rather than costs of matings themselves could also explain the results. In the present study, the fitness costs of male harassment for female C. maculatus are estimated. The natural refractory period of females immediately after their first mating is used to separate the cost of harassment from the cost of mating. Male harassment results in females laying fewer eggs and this results in a tendency to produce fewer offspring. The results are discussed in the context of mate choice and sexual selection. © 2008 the Royal Entomological Society.
Abstract.
Finn JK, Tregenza T, Norman MD (2009). Defensive tool use in a coconut-carrying octopus.
Curr Biol,
19(23), R1069-R1070.
Author URL.
Aarssen LW, Lortie CJ, Budden AE, Koricheva J, Leimu R, Tregenza T (2009). Does publication in top-tier journals affect reviewer behavior?.
PLoS One,
4(7).
Abstract:
Does publication in top-tier journals affect reviewer behavior?
We show that when ecologists act as reviewers their reported rejection rates recommended for manuscripts increases with their publication frequency in high impact factor journals. Rejection rate however does not relate to reviewer age. These results indicate that the likelihood of getting a paper accepted for publication may depend upon factors in addition to scientific merit. Multiple reviewer selection for a given manuscript therefore should consider not only appropriate expertise, but also reviewers that have variable publication experience with a range of different journals to ensure balanced treatment. Interestingly since age did not relate to rejection rates, more senior scientists are not necessarily more jaded in reviewing practices.
Abstract.
Author URL.
Gay L, Eady PE, Vasudev R, Hosken DJ, Tregenza T (2009). Does reproductive isolation evolve faster in larger populations via sexually antagonistic coevolution?.
Biol Lett,
5(5), 693-696.
Abstract:
Does reproductive isolation evolve faster in larger populations via sexually antagonistic coevolution?
Sexual conflict over reproductive investment can lead to sexually antagonistic coevolution and reproductive isolation. It has been suggested that, unlike most models of allopatric speciation, the evolution of reproductive isolation through sexually antagonistic coevolution will occur faster in large populations as these harbour greater levels of standing genetic variation, receive larger numbers of mutations and experience more intense sexual selection. We tested this in bruchid beetle populations (Callosobruchus maculatus) by manipulating population size and standing genetic variability in replicated lines derived from founders that had been released from sexual conflict for 90 generations. We found that after 19 generations of reintroduced sexual conflict, none of our treatments had evolved significant overall reproductive isolation among replicate lines. However, as predicted, measures of reproductive isolation tended to be greater among larger populations. We discuss our methodology, arguing that reproductive isolation is best examined by performing a matrix of allopatric and sympatric crosses whereas measurement of divergence requires crosses with a tester line.
Abstract.
Author URL.
Rodríguez-Muñoz R, Tregenza T (2009). Genetic compatibility and hatching success in the sea lamprey (Petromyzon marinus).
Biol Lett,
5(2), 286-288.
Abstract:
Genetic compatibility and hatching success in the sea lamprey (Petromyzon marinus).
Recent discussion of genetic benefits of polyandry and female mate choice has distinguished between two potential factors influencing offspring quality: (i) some males carry higher quality genes and (ii) males and females differ in their degree of genetic compatibility. We examined evidence for effects of good genes and genetic compatibility on embryonic survival of sea lamprey (Petromyzon marinus), a fish species with external fertilization that spawns in North Atlantic rivers. Using in vitro fertilization, we made all possible crosses among 10 males and 5 females collected in the spawning grounds. Male identity did not have any significant effect on hatching success. However, female identity and male x female interactions had a highly significant effect on hatching success. Our results suggest that genetic compatibility between male and female genomes plays an important role in embryo survival during the early stages of development in the sea lamprey.
Abstract.
Author URL.
Hosken DJ, Stockley P, Tregenza T, Wedell N (2009). Monogamy and the battle of the sexes.
Annu Rev Entomol,
54, 361-378.
Abstract:
Monogamy and the battle of the sexes.
Sexual conflict has been suggested to be important in the evolution of reproductive traits, with much recent theoretical and empirical evidence emphasizing its role in generating sexually antagonistic coevolution in the context of promiscuous mating. Here we shift attention to the role of sexual conflict in a monogamous mating context. Conflicts can arise, for example, when males are successful in imposing monandry at a cost to female fitness, or when females impose monogyny on males. Conflict over remating can also generate monogamy. For example, when males invest heavily in attempting to impose female monandry, the cost of their investment may prevent them from securing additional mates. We emphasize that sexual conflicts need not always generate sexually antagonistic coevolution, and that it is important to consider whether mating decisions are controlled primarily by males or females. Finally, we briefly discuss approaches to distinguish between conflict and classical modes of sexual selection, as this highlights difficulties associated with deciding whether monogamy is enforced by one sex or the other. We suggest that documenting the current fitness consequences of mate choice and mating patterns provides insight into the relative importance of classic and conflict modes of selection.
Abstract.
Author URL.
Brown EA, Gay L, Vasudev R, Tregenza T, Eady PE, Hosken DJ (2009). Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles. Heredity, 103(6), 340-345.
Brown EA, Gay L, Vasudev R, Tregenza T, Eady PE, Hosken DJ (2009). Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles.
Heredity (Edinb),
103(4), 340-345.
Abstract:
Negative phenotypic and genetic associations between copulation duration and longevity in male seed beetles.
Reproduction can be costly and is predicted to trade-off against other characters. However, while these trade-offs are well documented for females, there has been less focus on aspects of male reproduction. Furthermore, those studies that have looked at males typically only investigate phenotypic associations, with the underlying genetics often ignored. Here, we report on phenotypic and genetic trade-offs in male reproductive effort in the seed beetle, Callosobruchus maculatus. We find that the duration of a male's first copulation is negatively associated with subsequent male survival, phenotypically and genetically. Our results are consistent with life-history theory and suggest that like females, males trade-off reproductive effort against longevity.
Abstract.
Author URL.
Finn J, Tregenza T, Norman M (2009). Preparing the perfect cuttlefish meal: complex prey handling by dolphins.
PLoS One,
4(1).
Abstract:
Preparing the perfect cuttlefish meal: complex prey handling by dolphins.
Dolphins are well known for their complex social and foraging behaviours. Direct underwater observations of wild dolphin feeding behaviour however are rare. At mass spawning aggregations of giant cuttlefish (Sepia apama) in the Upper Spencer Gulf in South Australia, a wild female Indo-Pacific bottlenose dolphin (Tursiops aduncus) was observed and recorded repeatedly catching, killing and preparing cuttlefish for consumption using a specific and ordered sequence of behaviours. Cuttlefish were herded to a sand substrate, pinned to the seafloor, killed by downward thrust, raised mid-water and beaten by the dolphin with its snout until the ink was released and drained. The deceased cuttlefish was then returned to the seafloor, inverted and forced along the sand substrate in order to strip the thin dorsal layer of skin off the mantle, thus releasing the buoyant calcareous cuttlebone. This stepped behavioural sequence significantly improves prey quality through 1) removal of the ink (with constituent melanin and tyrosine), and 2) the calcareous cuttlebone. Observations of foraging dolphin pods from above-water at this site (including the surfacing of intact clean cuttlebones) suggest that some or all of this prey handling sequence may be used widely by dolphins in the region. Aspects of the unique mass spawning aggregations of giant cuttlefish in this region of South Australia may have contributed to the evolution of this behaviour through both high abundances of spawning and weakened post-spawning cuttlefish in a small area (>10,000 animals on several kilometres of narrow rocky reef), as well as potential long-term and regular visitation by dolphin pods to this site.
Abstract.
Author URL.
Bretman A, Newcombe D, Tregenza T (2009). Promiscuous females avoid inbreeding by controlling sperm storage.
Mol Ecol,
18(16), 3340-3345.
Abstract:
Promiscuous females avoid inbreeding by controlling sperm storage.
Recent studies in a variety of species have shown that polyandrous females are somehow able to bias paternity against their relatives postcopulation, although how they do so remains unknown. Field crickets readily mate with their siblings, but when also mated to an unrelated male, they produce disproportionately fewer inbred offspring. We use a new competitive microsatellite polymerase chain reaction technique to determine the contribution of males to stored sperm and subsequent paternity of offspring. Paternity is almost completely predicted by how much sperm from a particular male is stored, and unrelated males contribute more sperm to storage and have a corresponding higher paternity success.
Abstract.
Author URL.
Tregenza T, Attia F, Bushaiba SS (2009). Repeatability and heritability of sperm competition outcomes in males and females of Tribolium castaneum.
Behavioral Ecology and Sociobiology,
63(6), 817-823.
Abstract:
Repeatability and heritability of sperm competition outcomes in males and females of Tribolium castaneum
Differences among males in their success in achieving fertilisations when females mate with more than one partner are now recognised as an important target of sexual selection. However, very few studies have attempted to determine whether particular males are consistently successful in sperm competition and whether success in sperm competition is a heritable trait. Additionally, the potential heritability of female traits that influence the outcome of sperm competition has received only limited attention. Using the polyandrous beetle Tribolium castaneum, we examined repeatability of male success in sperm competition by mating pairs of males carrying different visible genetic markers to a string of different females. Males showed consistency in their ability to successfully transfer sperm to females, but not in their success in sperm competition. Furthermore, when we independently compared success in sperm competition of fathers with their sons, we found no evidence for heritability of this trait. Similarly, females that exhibited high or low first male sperm precedence did not tend to have daughters that showed the same pattern. Our results suggest that we should be wary of assuming that success in sperm competition is heritable through either sex. © 2009 Springer-Verlag.
Abstract.
Gay L, Hosken DJ, Vasudev R, Tregenza T, Eady PE (2009). Sperm competition and maternal effects differentially influence testis and sperm size in Callosobruchus maculatus.
J Evol Biol,
22(5), 1143-1150.
Abstract:
Sperm competition and maternal effects differentially influence testis and sperm size in Callosobruchus maculatus.
The evolutionary factors affecting testis size are well documented, with sperm competition being of major importance. However, the factors affecting sperm length are not well understood; there are no clear theoretical predictions and the empirical evidence is inconsistent. Recently, maternal effects have been implicated in sperm length variation, a finding that may offer insights into its evolution. We investigated potential proximate and microevolutionary factors influencing testis and sperm size in the bruchid beetle Callosobruchus maculatus using a combined approach of an artificial evolution experiment over 90 generations and an environmental effects study. We found that while polyandry seems to select for larger testes, it had no detectable effect on sperm length. Furthermore, population density, a proximate indicator of sperm competition risk, was not significantly associated with sperm length or testis size variation. However, there were strong maternal effects influencing sperm length.
Abstract.
Author URL.
Green K, Tregenza T (2009). The influence of male ejaculates on female mate search behaviour, oviposition and longevity in crickets.
Animal Behaviour,
77(4), 887-892.
Abstract:
The influence of male ejaculates on female mate search behaviour, oviposition and longevity in crickets
In animals with internal fertilization, sperm are transferred in ejaculates, which include water and proteins produced by male accessory glands. These proteins help to protect and facilitate sperm passage, and in some species have been identified as having an influence on female behaviour and life history traits. They may increase oviposition rate, reduce sexual receptivity and decrease female life span. Virgin female field crickets Gryllus bimaculatus orient and move towards calling song produced by males. However, phonotaxis is greatly reduced after mating. We tested the hypothesis that female phonotaxis, oviposition and longevity are influenced by compounds in male ejaculates. We divided females into two groups: one injected with seminal proteins extracted from spermatophores from which sperm had been removed, and one injected with Ringer's solution. We measured female egg laying and phonotaxis before and after treatment, and recorded female longevity. We did not detect an effect of treatment on either egg laying or phonotaxis. However, females treated with seminal proteins moved less overall and died sooner than females in the control group. We therefore failed to find any evidence that postmating reductions in phonotaxis are due to effects of male seminal proteins. However, the reduction in female movement after treatment with seminal proteins could reduce their likelihood of subsequent matings. © 2009 the Association for the Study of Animal Behaviour.
Abstract.
Borsuk RM, Aarssen LW, Budden AE, Koricheva J, Leimu R, Tregenza T, Lortie CJ (2009). To name or not to name: the effect of changing author gender on peer review.
BioScience,
59(11), 985-989.
Abstract:
To name or not to name: the effect of changing author gender on peer review
The peer review model is one of the most important tools used in science to assess the relative merit of research. We manipulated a published article to reflect one of the following four author designations: female, male, initial, and no name provided. This article was then reviewed by referees of both genders at various stages of scientific training. Name changing did not influence acceptance rates or quality ratings. Undergraduate referees were less critical than graduate students or postdoctoral researchers, independent of gender. However, female postdoctoral researchers were the most critical referees: Their rejection rates were the highest and quality ratings the lowest, regardless of the author name provided. Contrary to previous reports in the literature, there was no evidence of same-gender preferences. This study strongly suggests that female postgraduate biologists may apply different expectations to peer review. © 2009 by American Institute of Biological Sciences. All rights reserved.
Abstract.
2008
Edvardsson M, Rodríguez-Muñoz, R. Tregenza, T. (2008). 2008 No evidence that female Callosobruchus maculatus use remating to reduce costs of inbreeding. Animal Behaviour, 75, 1519-1524.
Rodríguez-Muñoz R, Ojanguren AF, Tregenza T (2008). Comment on "International conservation policy delivers benefits for birds in Europe".
Science,
319(5866).
Abstract:
Comment on "International conservation policy delivers benefits for birds in Europe".
Donald et al. (Reports, 10 August 2007, p. 810) assessed the impact of the European Union's Birds Directive, a conservation policy enacted in 1979, and reported evidence for positive population changes in targeted species. We argue that their conclusions are overstatements based on unsuitable data and inappropriate analyses.
Abstract.
Author URL.
Pincheira-Donoso D, Hodgson DJ, Tregenza T (2008). Comparative evidence for strong phylogenetic inertia in precloacal signalling glands in a species-rich lizard clade. Evolutionary Ecology Research, 10, 11-28.
Hodgson, D.J. Tregenza, T. (2008). Comparative evidence for strong phylogenetic inertia in precloacal signalling glands in a species-rich lizard clade.
Budden AE, Aarssen LW, Koricheva J, Leimu R, Lortie CJ, Tregenza T (2008). Does double-blind review favor female authors? Reply.
FRONTIERS IN ECOLOGY AND THE ENVIRONMENT,
6(7), 356-357.
Author URL.
Leimu R, Lortie CJ, Aarssen L, Budden AE, Koricheva J, Tregenza T (2008). Does it pay to have a "bigwig" as a co-author?. Frontiers in Ecology and the Environment, 6(8), 410-411.
Budden AE, Tregenza T, Aarssen W, Koricheva JK, Leimu R, Lortie CJ (2008). Double-blind review favours increased representation of female authors. Trends in Ecology & Evolution, 23, 4-6.
Budden, A.E. Tregenza, T, Aarssen, W. Koricheva, J.K. Leimu, R. Lortie, C. J. (2008). Double-blind review: Accept with minor revisions. Trends in Ecology & Evolution, 23, 353-354.
Leimu R, Lortie CJ, Tregenza T, Koricheva J, Budden AE, Aarssen L (2008). How big are bigwigs?: a reply to Havens. Frontiers in Ecology and the Environment, 6(10).
Wright, L, Tregenza, T. Hosken, D.J. (2008). Inbreeding, inbreeding depression and extinction. Conservation Genetics, 9, 833-843.
Smallegange IM, Tregenza T (2008). Local Competition Between Foraging Relatives: Growth and Survival of Bruchid Beetle Larvae.
J Insect Behav,
21(5), 375-386.
Abstract:
Local Competition Between Foraging Relatives: Growth and Survival of Bruchid Beetle Larvae.
Kin selection theory states that when resources are limited and all else is equal, individuals will direct competition away from kin. However, when competition between relatives is completely local, as is the case in granivorous insects whose larval stages spend their lives within a single seed, this can reduce or even negate the kin-selected benefits. Instead, an increase in competition may have the same detrimental effects on individuals that forage with kin as those that forage with non-kin. In a factorial experiment we assessed the effects of relatedness and competition over food on the survival and on fitness-related traits of the bruchid beetle Callosobruchus maculatus. Relatedness of competitors did not affect the survival of larvae. Larval survival substantially decreased with increasing larval density, and we found evidence that beetles maturing at a larger size were more adversely affected by competition, resulting in lower survival rates. Furthermore, females showed a reduction in their growth rate with increasing larval density, emerging smaller after the same development time. Males increased their growth rate, emerging earlier but at a similar size when food was more limited. Our results add to the growing number of studies that fail to show a relationship between relatedness and a reduction in competition between relatives in closed systems, and emphasize the importance of the scale at which competition between relatives occurs.
Abstract.
Author URL.
Bretman, A, Dawson, D.A. Horsburgh, G.J. Tregenza, T. (2008). New microsatellite loci isolated from the field cricket <em>Gryllus bimaculatus</em> characterized in two cricket species, <em>Gryllus bimaculatus</em> and <em>Gryllus campestris</em>. Molecular Ecology Resources, 3, 191-195.
Edvardsson M, Rodríguez-Muñoz R, Tregenza T (2008). No evidence that female bruchid beetles, Callosobruchus maculatus, use remating to reduce costs of inbreeding.
Animal Behaviour,
75(4), 1519-1524.
Abstract:
No evidence that female bruchid beetles, Callosobruchus maculatus, use remating to reduce costs of inbreeding
Despite the often dramatic negative effects of inbreeding on offspring fitness, matings between closely related individuals sometimes occur. This may be because females cannot reliably recognize related males before mating with them. As an alternative to precopulatory choice, polyandrous females may avoid inbreeding through postcopulatory mechanisms if they can assess mate relatedness during or after copulation. These mechanisms include increasing remating propensity and decreasing rate of offspring production in response to incestuous matings. Stored product pests, such as the bruchid beetle Callosobruchus maculatus, have an ecology that is likely to expose them to frequent risks of inbreeding when a small number of females found a new population on a previously uninfested store of beans. Using this species, we show that inbreeding has negative effects on offspring viability but that females do not appear to discriminate between brothers and unrelated males prior to mating. Furthermore, females that first mated with brothers did not increase their remating propensity or decrease their rate of offspring production relative to females that first mated with unrelated males. Our findings suggest that the costs of inbreeding have not been sufficient to drive the evolution of mating behaviour as a mechanism of inbreeding avoidance in C. maculatus. © 2007 the Association for the Study of Animal Behaviour.
Abstract.
Tregenza, T. Simmons, L.W. (2008). Nuptial gifts fail to resolve a sexual conflict in an insect. BMC Evolutionary Biology, 8
Budden AE, Lortie CJ, Tregenza T, Aarssen L, Koricheva J, Leimu R (2008). Response to Webb et al.: Double-blind review: accept with minor revisions. Trends in Ecology and Evolution, 23(7), 353-354.
Budden AE, Aarssen L, Koricheva J, Leimu R, Lortie CJ, Tregenza T (2008). Response to Whittaker: challenges in testing for gender bias. Trends in Ecology and Evolution, 23(9), 480-481.
Rodríguez-Muñoz R, Bretman A, Hadfield JD, Tregenza T (2008). Sexual selection in the cricket <em>Gryllus bimaculatus</em>: No good genes?. Genetica, 132, 287-294.
Rodríguez-Muñoz R, Bretman A, Hadfield JD, Tregenza T (2008). Sexual selection in the cricket Gryllus bimaculatus: no good genes?.
Genetica,
134(1), 129-136.
Abstract:
Sexual selection in the cricket Gryllus bimaculatus: no good genes?
Recent studies have suggested that females of the field cricket Gryllus bimaculatus exercise post-copulatory choice over the paternity of their offspring. There is evidence that these choices are made in relation to the genetic compatibility of mates rather than their absolute quality, but the magnitude of heritable differences in males has not been thoroughly examined. Using a half-sib breeding design we measured additive genetic variance and dam effects in a suite of reproductive and non-reproductive traits. Both components explained relatively little of the phenotypic variance across traits. The dam component in our design contains variance caused by both maternal effects and dominance. If maternal effects are negligible as suggested by previous studies, our data suggest that dominance variance is an important source of variation in these traits. The lack of additive genetic variation, but possible existence of large amounts of non-additive genetic variation is consistent with the idea that female mate choice and multiple mating may be driven by differences in genetic compatibility between potential mates rather than by differences in genetic quality.
Abstract.
Author URL.
Grod ON, Budden AE, Tregenza T, Koricheva J, Leimu R, Aarssen LW, Lortie CJ (2008). Systematic variation in reviewer practice according to country and gender in the field of ecology and evolution.
PLoS One,
3(9).
Abstract:
Systematic variation in reviewer practice according to country and gender in the field of ecology and evolution.
The characteristics of referees and the potential subsequent effects on the peer-review process are an important consideration for science since the integrity of the system depends on the appropriate evaluation of merit. In 2006, we conducted an online survey of 1334 ecologists and evolutionary biologists pertaining to the review process. Respondents were from Europe, North America and other regions of the world, with the majority from English first language countries. Women comprised a third of all respondents, consistent with their representation in the scientific academic community. Among respondents we found no correlation between the time typically taken over a review and the reported average rejection rate. On average, Europeans took longer over reviewing a manuscript than North Americans, and females took longer than males, but reviewed fewer manuscripts. Males recommended rejection of manuscripts more frequently than females, regardless of region. Hence, editors and potential authors should consider alternative sets of criteria, to what exists now, when selecting a panel of referees to potentially balance different tendencies by gender or region.
Abstract.
Author URL.
Budden AE, Aarssen LW, Koricheva J, Leimu R, Lortie CJ, Tregenza T (2008). The authors respond. Frontiers in Ecology and the Environment, 6(7), 354-355.
Pincheira-Donoso D, Hodgson DJ. Tregenza T (2008). The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards?. BMC Evolutionary Biology, 8
2007
Cornell S, Tregenza T (2007). A new theory for the evolution of polyandry as a means of inbreeding avoidance. Proceedings of the Royal Society B, 274, 2873-2879.
Tregenza, T. Hodgson, D.J. (2007). Body size evolution in South American Liolaemus lizards of the boulengeri clade: a contrasting reassessment. Journal of Evolutionary Biology, 20, 2067-2071.
Rodríguez-Muñoz R, Mirol PM, Segelbacher G, Ferná, ndez A, Tregenza T (2007). Genetic differentiation of an endangered capaercallie (<em>Tetrao urogallus</em>) population at the Southern edge of the species range. Conservation Genetics, 8, 659-670.
Edvardsson M, Champion de Crespigny FE, Tregenza T (2007). Mating behaviour: promiscuous mothers have healthier young.
Curr Biol,
17(2), R66-R67.
Abstract:
Mating behaviour: promiscuous mothers have healthier young.
A small marsupial has thrown new light on the question of why females typically mate with several males: promiscuous female antechinuses have many more surviving offspring because males that are successful in sperm competition also sire healthy offspring.
Abstract.
Author URL.
Tregenza, T. (2007). Mimicry as deceptive resemblance: beyond the one-trick ponies. In Dautenhahnand K, Nehaniv CL (Eds.)
Imitation and Social Learning in Robots, Humans and Animals: Behavioural, Social and Communicative Dimensions, Cambridge: Cambridge University Press, 441-453.
Author URL.
Lortie CJ, Aarssen LW, Budden AE, Korichva JK, Leimu R, Tregenza T (2007). Publication bias and merit in ecology. Oikos, 116, 1247-1253.
Lortie CJ, Aarssen LW, Budden AE, Koricheva JK, Leimu R, Tregenza T (2007). Publication bias and merit in ecology.
Oikos,
116(7), 1247-1253.
Abstract:
Publication bias and merit in ecology
Bias, or any set of factors that influence the general expression of merit, is common in science and is an inevitable by‐product of an imperfect but otherwise reasonably objective human pursuit to understand the world we inhabit. In this paper, we explore the conceptual significance of a relatively tractable form of bias, namely publication and dissemination bias. A specific definition is developed, a working model of classification for publication bias is proposed, and an assessment of what we can measure is described. Finally, we offer expectations for ecologists with respect to the significance of bias in the publication process within our discipline. We argue that without explicit consideration of both the qualitative and quantitative aspects of publication bias in ecology, we limit our capacity to fairly assess and best use the science that we as a community produce.
Abstract.
Ritchie MG (2007). Sexual selection and speciation. In (Ed)
ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS, 79-102.
Author URL.
Bretman A, Tregenza T (2007). Strong, silent types: the rapid, adaptive disappearance of a sexual signal.
Trends Ecol Evol,
22(5), 226-228.
Abstract:
Strong, silent types: the rapid, adaptive disappearance of a sexual signal.
To see evolution in action, it helps to be in the right place at the right time. In a recent study, Zuk et al. document the rapid evolution of a sexual signal in crickets on a Hawaiian island and suggest that it is a response to parasitism. A new male morph has appeared that cannot sing, and so does not attract an acoustically orientating parasite. The disadvantage of this, however, is that silent males might not be able to attract mates. The authors suggest that plasticity in male aggregating behaviour can provide an escape from the costs of this potentially maladaptive trait.
Abstract.
Author URL.
2006
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies.
SCIENCE,
312(5774), 689-690.
Author URL.
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies [2]. Science, 312(5774), 689-690.
Shuker DM, Tregenza T (2006). Debating sexual selection and mating strategies [9]. Science, 312(5774), 693-694.
Shuker DM, Tregenza T (2006). Debating sexual selection and mating strategies.
Science,
312(5774), 689-697.
Author URL.
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies.
Science,
312(5774), 689-697.
Author URL.
Hosken, DJ, Tregenza, T. (2006). Evolution; Inbreeding, Multiple mating and Embryonic Aid. Current Biology, 16(6), R202-R203.
Tregenza, T. Simmons, L.W. Wedell, N. & Zuk, M. (2006). Female preference for male courtship song and its role as a signal of immune function and condition. Animal Behaviour, 72, 809-118.
Tregenza T, Wedell N, Chapman T (2006). Introduction. Sexual conflict: a new paradigm?.
Philos Trans R Soc Lond B Biol Sci,
361(1466), 229-234.
Author URL.
Rodríguez-Muñoz, R. Tregenza, T. (2006). Male dominance determines female egg laying rate in crickets. Biology Letters, 2, 409-411.
Wedell, N. Beveridge, M. Tregenza, T. (2006). Post-copulatory inbreeding avoidance by female crickets only revealed by molecular markers. Molecular Ecology, 15(12), 3817-3824.
Shuker D & Tregenza T (2006). Reply to Roughgarden - Sexual selection happens. Science, 312, 693-694.
Wedell, N. Chapman, T.C. (2006). Sexual conflict - a new paradigm?. Philosophical Transactions of the Royal Society, 361, 229-234.
Kvarnemo, L. Lessells, C.M. Tregenza (2006). Sexual conflict and life histories. Animal Behaviour, 71, 999-1011.
2005
Hosken DJ, Tregenza T (2005). Evolution: do bad husbands make good fathers?.
Curr Biol,
15(20), R836-R838.
Abstract:
Evolution: do bad husbands make good fathers?
Males sometimes harm their mates as they seek to maximise the number of offspring they sire. But are females really suffering or do the benefits of having sons that inherit their father's manipulative traits make up for the costs? Three recent studies provide the first hard data addressing this issue, but they differ in their conclusions.
Abstract.
Author URL.
Hosken, D.J. Tregenza, T (2005). Mate choice; Been there, done that. Current Biology, 15(23), R959-R961.
Tregenza T, Bretman AJ (2005). Measuring polyandry in wild populations: a case study using promiscuous crickets. Molecular Ecology, 14(7), 2169-2179.
Tregenza, T. Hosken DJ (2005). Sexual selection: Do bad husbands make good fathers?. Current Biology, 15(20), R836-R838.
Butlin RK, Tregenza T (2005). The way the world might be.
J Evol Biol,
18(5), 1205-1208.
Author URL.
Tregenza, T. (2005). Why do male <em>Callosobruchus maculatus</em> harm their mates?. Behavioral Ecology, 16, 788-793.
2004
Tregenza, T. (2004). Divergence revealed by population crosses in the red flour beetle <em>Tribolium castaneum</em>. Evolutionary Ecology Research, 6, 927-935.
Radwan, J. Kotiaho, J.S. (2004). Genic capture and resolving the lek paradox. Trends in Ecology & Evolution, 19, 323-328.
Bretman AJ, Wedell N, Tregenza T (2004). Molecular evidence of post-copulatory inbreeding avoidance in the field cricket Gryllus bimaculatus. Proceedings of the Royal Society B Biological Sciences, 271(1535), 159-164.
Wedell, N. (2004). Proceedings of the Royal Society B 271, 'Molecular evidence of post-copulatory inbreeding avoidance in the field cricket <em>Gryllus bimaculatus</em>'. , 159-164.
2003
Tregenza T (2003). Evolution: the battle between the sexes.
Nature,
423(6943), 929-930.
Author URL.
Tregenza T, Hosken DJ, Ward PI, Wedell N (2003). Maternal effects on offspring depend on female mating pattern and offspring environment in yellow dung flies. Evolution, 57(2), 297-304.
Bretman, A.J. Tregenza, T. (2003). Microsatellite loci for the field cricket, <em>Gryllus bimaculatus</em> and their cross-utility in other species of Orthoptera. Molecular Ecology Notes, 3, 191-195.
Hosken DJ, Garner, T.W.J. Tregenza, T. Wedell N, Ward PI (2003). Superior sperm competitors sire higher quality young. Proceedings of the Royal Society of London B, 270, 1933-1938.
Tregenza, T. (2003). The battle between the sexes. Nature, 423, 929-930.
Tregenza, T. Butlin, R.K. (2003). Transitions in cuticular composition across a hybrid zone – historical accident or environmental adaptation?. Biological Journal of the Linnean Society, 78, 193-201.
2002
Tregenza, T. (2002). Divergence and reproductive isolation in the early stages of speciation. Genetica, 116, 291-300.
Finn, J. Paul, D. (2002). Extreme sexual size dimorphism. New Zealand Journal of Freshwater and Marine Biology, 36, 733-736.
Norman MD, Paul D, Finn J, Tregenza T (2002). First encounter with a live male blanket octopus: the world's most sexually size-dimorphic large animal.
New Zealand Journal of Marine and Freshwater Research,
36(4), 733-736.
Abstract:
First encounter with a live male blanket octopus: the world's most sexually size-dimorphic large animal
The first encounter with a live male blanket octopus, Tremoctopus violaceus Chiaie, 1830, illustrates the most extreme example of sexual size-dimorphism in a non-microscopic animal. Females attain sizes of up to 2 m long—almost 2 orders of magnitude larger than the 2.4-cm-long male. Weight ratios between the sexes are at least 10 000:1 and are likely to reach 40 000:1. Sexual selection and the unique defensive strategy of carrying cnidarian stinging tentacles may both have contributed to the evolution of this extreme size-dimorphism. Such dimorphism is not seen in any other animal remotely as large. © 2002, Copyright Taylor & Francis Group, LLC.
Abstract.
Tregenza, T. (2002). Gender bias in the refereeing process?. Trends in Ecology & Evolution, 349-350.
Ward PI, Wedell, N. Hosken, D.J. Tregenza T (2002). Measuring the sperm competition successes of field males of the yellow dung fly. Ecological Entomology, 27, 763-765.
Tregenza, T. Wedell, N. (2002). Oviposition preference and geographic specialization by the mrymecophilous butterfly <em>Jalmenus evagoras</em> (Lepidoptera: Lycaenidae) in response to attendant ants. Journal of Evolutionary Biology, 15, 861-870.
Fraser AM, Tregenza T, Wedell N, Elgar MA, Pierce NE (2002). Oviposition tests of ant preference in a myrmecophilous butterfly.
Journal of Evolutionary Biology,
15(5), 861-870.
Abstract:
Oviposition tests of ant preference in a myrmecophilous butterfly
Butterflies in the family Lycaenidae that have obligate associations with ants frequently exhibit ant-dependent egg laying behaviour. In a series of field and laboratory choice tests, we assessed oviposition preference of the Australian lycaenid Jalmenus evagoras in response to different species and populations of ants. Females discriminated between attendant and nonattendant ant species, between attendant ant species, and to some extent, between populations of a single ant species. When preferences were found, ovipositing butterflies preferred their locally predominant attendant ant species and geographically proximate attendant ant populations. A reciprocal choice test using adults from a generation of butterflies reared in the absence of ants indicated a genetic component to oviposition preference. Individual females were flexible with respect to oviposition site choice, often ovipositing on more than one treatment during a trial. Preferences arose from a hierarchical ranking of ant treatments. These results are discussed in terms of local adaptation and its possible significance in the diversification of ant-associated lycaenids.
Abstract.
Tregenza T, Wedell N (2002). Polyandrous females avoid costs of inbreeding. Nature, 415(6867), 71-73.
Pritchard, V.L. Butlin, R.K. (2002). The origins of postmating reproductive isolation: testing hypotheses in the grasshopper <em>Chorthippus parallelus</em>. Population Ecology, 44, 137-144.
2001
Finn, J. Tregenza, T. (2001). Dynamic mimicry in an Indo-Malayan octopus. Proceedings of the Royal Society B, 268, 1755-1758.
Butlin, R.K. Zuk, M. (2001). Sexual selection and speciation. Trends in Ecology & Evolution, 16, 364-371.
2000
Liimatainen, J.O. Tregenza, T. Hoikkala, A. (2000). Courtship signals and mate choice of the flies of inbred <em>Drosophila montana</em> strains. Journal of Evolutionary Biology, 13, 583-592.
Payne RJH, Krakauer DC (2000). Disruptive sexual selection.
TRENDS IN ECOLOGY & EVOLUTION,
15(10), 419-420.
Author URL.
Bridle JR, Jiggins CD, Tregenza T (2000). Disruptive sexual selection - Reply.
TRENDS IN ECOLOGY & EVOLUTION,
15(10), 420-420.
Author URL.
Payne RJH, Krakauer DC, Bridle JR, Jiggins CD, Tregenza T (2000). Disruptive sexual selection [3] (multiple letters). Trends in Ecology and Evolution, 15(10), 419-420.
Butlin RK, Tregenza T (2000). Erratum: Levels of genetic polymorphism: Marker loci versus quantitative traits (Phil. Trans. R. Soc. Lond. B (February 1998) 353 (187-198)). Philosophical Transactions of the Royal Society B: Biological Sciences, 355(1404).
Tregenza, T. (2000). Evolutionarily dynamic sperm. Trends in Ecology & Evolution, 15, 85-86.
Tregenza T, Butlin RK, Wedell N (2000). Evolutionary biology: Sexual conflict and speciation. Nature, 407(6801), 149-150.
Tregenza T, Wedell N (2000). Genetic compatibility, mate choice and patterns of parentage: invited review.
Mol Ecol,
9(8), 1013-1027.
Abstract:
Genetic compatibility, mate choice and patterns of parentage: invited review.
There is growing interest in the possibility that genetic compatibility may drive mate choice, including gamete choice, particularly from the perspective of understanding why females frequently mate with more than one male. Mate choice for compatibility differs from other forms of choice for genetic benefits (such as 'good genes') because individuals are expected to differ in their mate preferences, changing the evolutionary dynamics of sexual selection. Recent experiments designed to investigate genetic benefits of polyandry suggest that mate choice on the basis of genetic compatibility may be widespread. However, in most systems the mechanisms responsible for variation in compatibility are unknown. We review potential sources of variation in genetic compatibility and whether there is any evidence for mate choice driven by these factors. Selfish genetic elements appear to have the potential to drive mate compatibility mate choice, though as yet there is only one convincing example. There is abundant evidence for assortative mating between populations in hybrid zones, but very few examples where this is clearly a result of selection against mating with genetically less compatible individuals. There are also numerous cases of inbreeding avoidance, but little evidence that mate choice or differential fertilization success driven by genetic compatibility occurs between unrelated individuals. The exceptions to this are a handful of situations where both the alleles causing incompatibility and the alleles involved in mate choice are located in a chromosome region where recombination is suppressed. As yet there are only a few potential sources of genetic compatibility which have clearly been shown to drive mate choice. This may reflect limitations in the potential for the evolution of mate choice for genetic compatibility within populations, although the most promising sources of such incompatibilities have received relatively little research.
Abstract.
Author URL.
Buckley, S.H. Pritchard, V.L. Butlin, R.K. (2000). Inter- and intrapopulation effects of sex and age on epicuticular composition of meadow grasshopper, <em>Chorthippus parallelus</em>. Journal of Chemical Ecology, 26, 257-278.
Butlin RK, Tregenza T (2000). Levels of genetic polymorphism: marker loci versus quantitative traits (vol B353, pg 187, 1998).
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES,
355(1404), 1865-1865.
Author URL.
Tregenza T, Pritchard VL, Butlin RK (2000). Patterns of trait divergence between populations of the meadow grasshopper, Chorthippus parallelus.
Evolution,
54(2), 574-585.
Abstract:
Patterns of trait divergence between populations of the meadow grasshopper, Chorthippus parallelus.
To understand the process of speciation, we need to identify the evolutionary phenomena associated with divergence between populations of the same species. A powerful approach is to compare patterns of trait differences between populations differing in their evolutionary histories. A recent study of genetic divergence between populations of the meadow grasshopper Chorthippus parallelus, from different locations around Europe has allowed us to use this species to investigate which aspects of evolutionary history are associated with divergence in morphology and mating signals. During the last glaciation C. parallelus was confined to a number of refugia in southern Europe and has subsequently recolonized the northern part of the continent. This process of isolation followed by range expansion has created populations differing markedly in their evolutionary pasts--some have been isolated from one another for thousands of years, others have undergone repeated founder events, and others now live in sympatry with a closely related species. Using laboratory-reared grasshoppers from 12 different populations with a range of evolutionary histories, we quantify differences in morphology, chemical signals, and male calling-song. The observed pattern of divergence between these populations is then compared with the pattern predicted by hypotheses about what drives divergence. This comparison reveals that long periods in allopatry and processes associated with repeated founder events are both strongly associated with divergence.
Abstract.
Author URL.
Jiggins, C. Tregenza, T. (2000). Reply to Payne and Krakauer. Trends in Ecology & Evolution, 15
Tregenza T, Butlin RK, Wedell N (2000). Sexual conflict and speciation.
Nature,
407(6801), 149-150.
Author URL.
Wedell, N. Butlin, R.K. (2000). Speciation and sexual conflict. Nature, 407, 149-150.
Pritchard, V.L. Butlin, R.K. (2000). The origins of premating reproductive isolation: testing hypotheses in the grasshopper <em>Chorthippus parallelus</em>. Evolution, 54, 1687-1698.
1999
Finn, J. Tregenza, T. (1999). Female impersonation as an alternative reproductive strategy in giant cuttlefish. Proceedings of the Royal Society B, 266, 1347-1349.
Tregenza T, Butlin RK (1999). Erratum: Speciation without isolation (Nature (1999) 400 (311-312)). Nature, 400(6744).
Tregenza T & Butlin RK (1999). Genetic diversity: Do marker genes tell us the whole story?. In Magurran AE, May RM (Eds.) Evolution of Biological Diversity, 37-55.
Wedell N, Tregenza T (1999). SUCCESSFUL FATHERS SIRE SUCCESSFUL SONS.
Evolution,
53(2), 620-625.
Abstract:
SUCCESSFUL FATHERS SIRE SUCCESSFUL SONS.
The theory of sexual selection holds a central role in evolutionary biology. Its key assumption is the heritability of traits associated with reproductive success. Strong indirect evidence supporting this assumption comes from the numerous studies that have identified heritable traits associated with mating success. However, there remain only a handful of studies that have attempted to demonstrate directly that successful fathers have successful sons. We present the results of an experimental study of the mating success and phenotype of male field crickets Gryllus bimaculatus (Orthoptera: Gryllidae) and their offspring. These reveal that sons of successful males obtain significantly more copulations than sons of unsuccessful males. There was no difference in body size of sons of either group, but sons of successful males had significantly longer development times. This may represent a naturally selected cost to traits associated with success that could balance their sexually selected advantages.
Abstract.
Author URL.
Butlin, R.K. (1999). Speciation without isolation. Nature, 400, 311-312.
Tregenza T, Butlin RK (1999). Speciation without isolation (vol 400, pg 311, 1999).
NATURE,
400(6744), 513-513.
Author URL.
Tregenza, T. (1999). Successful fathers sire successful sons. Evolution, 53, 620-625.
1998
Tregenza T, Wedell N (1998). BENEFITS OF MULTIPLE MATES IN THE CRICKET GRYLLUS BIMACULATUS.
Evolution,
52(6), 1726-1730.
Abstract:
BENEFITS OF MULTIPLE MATES IN THE CRICKET GRYLLUS BIMACULATUS.
Despite the importance of polyandry for sexual selection, the reasons why females frequently mate with several males remain poorly understood. A number of genetic benefits have been proposed, based on the idea that by taking multiple mates, females increase the likelihood that their offspring will be sired by genetically more compatible or superior males. If certain males have intrinsically "good genes," any female mating with them will produce superior offspring. Alternatively, if some males have genetic elements that are incompatible with a particular female, then she may benefit from polyandry if the sperm of such males are less likely to fertilize her eggs. We examined these hypotheses in the field cricket Gryllus bimaculatus (Orthoptera: Gryllidae). By allocating females identical numbers of matings but different numbers of mates we investigated the influence of number of mates on female fecundity, and both short- and long-term offspring fitness. This revealed no effect of number of mates on number of eggs laid. However, hatching success of eggs increased with number of mates. This effect could not be attributed to nongenetic effects such as the possibility that polyandry reduces variance in the quantity or fertilizing ability of sperm females receive, because a control group receiving half the number of copulations showed no drop in hatching success. Offspring did not differ in survival, adult mass, size, or development time with treatment. When males were mated to several different females there were no repeatable differences between individual males in the hatching success of their mate's eggs. This suggests that improved hatching success of polyandrous females is not due to certain males having genes that improve egg viability regardless of their mate. Instead, our results support the hypothesis that certain males are genetically more compatible with certain females, and that this drives polyandry through differential fertilization success of sperm from more compatible males.
Abstract.
Author URL.
Wedell, N. (1998). Benefits of multiple mates in the cricket <em>Gryllus bimaculatus</em>. Evolution, 52, 1726-1730.
Tregenza, T. (1998). Levels of genetic polymorphism: marker loci versus quantitative traits. Philosophical Transactions of the Royal Society, 353, 187-198.
Parker GA, Partridge L (1998). Sexual conflict and speciation.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES,
353(1366), 261-274.
Author URL.
Thompson, D.J. (1998). Unequal competitor ideal free distribution in fish?. Evolution and Ecology, 12, 655-666.
1997
Tregenza, T. (1997). Alphabetical orders. Nature, 388
Tregenza, T. (1997). Darwin a better name than Wallace?. Nature, 385
Wedell, N. (1997). Definitive evidence for cuticular pheromones in a cricket. Animal Behaviour, 54, 979-984.
Butlin RK, Tregenza T (1997). Evolutionary biology - is speciation no accident?.
NATURE,
387(6633), 551-&.
Author URL.
Tregenza, T. (1997). Is speciation no accident?. Nature, 387, 551-552.
Wedell, N. (1997). Natural selection bias?. Nature, 386
Tregenza, T. Butlin, R.K. (1997). Speciation and signal trait genetics. Trends in Ecology & Evolution, 12, 299-301.
Bridle, J.R. (1997). The diversity of speciation. Trends in Ecology & Evolution, 12, 382-383.
Tregenza T (1997). What's up, doc?. New Scientist, 155(2099).
1996
Shaw, J.J. Thompson, D.J. (1996). An experimental investigation of a new ideal free distribution model. Evolution and Ecology, 10, 45-49.
Parker, G.A. Thompson, D.J. (1996). Interference and the ideal free distribution: Models and tests. Behavioral Ecology, 7, 379-386.
Thompson, D.J. Parker, G.A. (1996). Interference and the ideal free distribution: Oviposition in a parasitoid wasp. Behavioral Ecology, 7, 387-394.
Tregenza T, Hack MA, Thompson DJ (1996). Relative competitive success of unequal competitors changes with overall density.
OIKOS,
77(1), 158-162.
Author URL.
Hack, M.A. Thompson, D.J. (1996). Relative success of unequal competitors changes with overall density. Oikos, 77, 158-162.
1995
Tregenza, T. (1995). Building on the ideal free distribution. Adv.Ecol.Res, 26, 253-302.
TREGENZA T (1995). DREAM TEAMS.
NEW SCIENTIST,
148(2000), 59-59.
Author URL.
Tregenza, T. Parker, G.A. Harvey, I.F. (1995). Evolutionarily stable foraging speeds in feeding scrambles: a model and an experimental test. Proceedings of the Royal Society B, 260, 273-277.
1994
Tregenza, T. (1994). Common misconceptions in applying the ideal free distribution. Animal Behaviour, 47, 485-487.
