Aim: Correlative models that forecast extinction risk from climate change and invasion risks following species introductions, depend on the assumption that species’ current distributions reflect their climate tolerances (‘climatic equilibrium’). This assumption has rarely been tested with independent distribution data, and studies that have done so have focused on species that are widespread or weedy in their native range. We use independent data to test climatic equilibrium for a broadly representative group of species, and ask whether there are any general indicators that can be used to identify when equilibrium occurs.

Location: Europe and contiguous USA.

Methods: We contrasted the climate conditions occupied by 51 plant species in their native (European) and naturalized (USA) distributions by applying kernel smoothers to species’ occurrence densities. We asked whether species had naturalized in climate conditions that differ from their native ranges, suggesting climatic disequilibrium in the native range, and whether characteristics of species’ native distributions correspond with climatic equilibrium.

Results: a large proportion of species’ naturalized distributions occurred outside the climatic conditions occupied in their native ranges: for 22 species, the majority of their naturalized ranges fell outside their native climate conditions. Our analyses revealed large areas in Europe that species do not occupy, but which match climatic conditions occupied in the USA, suggesting a high degree of climatic disequilibrium in the native range. Disequilibrium was most severe for species with native ranges that are small and occupy a narrow range of climatic conditions.

Main conclusions: Our results demonstrate that the direct effects of climate on species distributions have been widely overestimated, and that previous large-scale validations of the equilibrium assumption using species’ native and naturalized distributions are not generally applicable. Non-climatic range limitations are likely to be the norm, rather than the exception, and pose added risks for species under climate change.

The current distributions of species are often assumed to correspond with the total set of environmental conditions under which species can persist. When this assumption is incorrect, extinction risk estimated from species distribution models can be misleading. The degree to which species can tolerate or even thrive under conditions found beyond their current distributions alters extinction risks, time lags in realizing those risks, and the usefulness of alternative management strategies. To inform these issues, we propose a conceptual framework within which empirical data could be used to generate hypotheses regarding the realized, fundamental, and ‘tolerance’ niche of species. Although these niche components have rarely been characterized over geographic scales, we suggest that this could be done for many plant species by comparing native, naturalized, and horticultural distributions.

Many non-native plants in the US have become problematic invaders of native and managed ecosystems, but a new generation of invasive species may be at our doorstep. Here, we review trends in the horticultural trade and invasion patterns of previously introduced species and show that novel species introductions from emerging horticultural trade partners are likely to rapidly increase invasion risk. At the same time, climate change and water restrictions are increasing demand for new types of species adapted to warm and dry environments. This confluence of forces could expose the US to a range of new invasive species, including many from tropical and semiarid Africa as well as the Middle East. Risk assessment strategies have proven successful elsewhere at identifying and preventing invasions, although some modifications are needed to address emerging threats. Now is the time to implement horticulture import screening measures to prevent this new wave of plant invasions.

Forecasts of species endangerment under climate change usually ignore the processes by which species ranges shift. By analysing the 'climate paths' that range shifts might follow, and two key range-shift processes--dispersal and population persistence--we show that short-term climatic and population characteristics have dramatic effects on range-shift forecasts. By employing this approach with 15 amphibian species in the western USA, we make unexpected predictions. First, inter-decadal variability in climate change can prevent range shifts by causing gaps in climate paths, even in the absence of geographic barriers. Second, the hitherto unappreciated trait of persistence during unfavourable climatic conditions is critical to species range shifts. Third, climatic fluctuations and low persistence could lead to endangerment even if the future potential range size is large. These considerations may render habitat corridors ineffectual for some species, and conservationists may need to consider managed relocation and augmentation of in situ populations.

Managed relocation (MR) has rapidly emerged as a potential intervention strategy in the toolbox of biodiversity management under climate change. Previous authors have suggested that MR(also referred to as assisted colonization, assisted migration, or assisted translocation) could be a last-alternative option after interrogating a linear decision tree. We argue that numerous interacting and value-laden considerations demand a more inclusive strategy for evaluating MR. The pace of modern climate change demands decision making with imperfect information, and tools that elucidate this uncertainty and integrate scientific information and social values are urgently needed. We present a heuristic tool that incorporates both ecological and social criteria in a multidimensional decision-making framework. For visualization
purposes, we collapse these criteria into 4 classes that can be depicted in graphical 2-D space. This framework offers a pragmatic approach for summarizing key dimensions of MR: capturing uncertainty in the evaluation criteria, creating transparency in the
evaluation process, and recognizing the inherent tradeoffs that different stakeholders bring to evaluation of MR and its alternatives.

1. Large-scale conservation planning requires the identification of priority areas in which species have a high likelihood of long-term persistence. This typically requires high spatial resolution data on species and their habitat. Such data are rarely available at a large geographical scale, so distribution modelling is often required to identify the locations of priority areas. However, distribution modelling may be difficult when a species is either not recorded, or not present, at many of the locations that are actually suitable for it. This is an inherent problem for species that exhibit metapopulation dynamics.

2. Rather than basing species distribution models on species locations, we investigated the consequences of predicting the distribution of suitable habitat, and thus inferring species presence/absence. We used habitat surveys to define a vegetation category which is suitable for a threatened species that has spatially dynamic populations (the butterfly Euphydryas aurinia), and used this as the response variable in distribution models. Thus, we developed a practical strategy to obtain high resolution (1 ha) large scale conservation solutions for E. aurinia
in Wales, UK.

3. Habitat-based distribution models had high discriminatory power. They could generalize over a large spatial extent and on average predicted 86% of the current distribution of E. aurinia in Wales. Models based on species locations had lower discriminatory power and were poorer at generalizing throughout Wales.

4. Surfaces depicting the connectivity of each grid cell were calculated for the predicted distribution of E. aurinia habitat. Connectivity surfaces provided a distance-weighted measure of the concentration of habitat in the surrounding landscape, and helped identify areas where the persistence of E. aurinia populations is expected to be highest. These identified successfully known areas of high conservation priority for E. aurinia. These connectivity surfaces allow conservation planning to take into account long-term spatial population dynamics, which would be impossible without being able to predict the species’ distribution over a large spatial extent.

5. Synthesis and applications. Where species location data are unsuitable for building high resolution predictive habitat distribution models, habitat data of sufficient quality can be easier to collect. We show that they can perform as well as or better than species data as a response variable. When coupled with a technique to translate distribution model predictions into landscape priority (such as connectivity calculations), we believe this approach will be a powerful tool for large-scale conservation planning.

. Species shifting their ranges under climate change are a conservation dilemma. Range-shifters may be threatened by climate change in their historic range. However range-shifters are likely to be generalist opportunists, which could mean they could harm aspects of biodiversity in their new ecosystems. Therefore, we need approaches to rapidly assess how range-shifters may integrate into the community of historically resident species.

2. The small red-eyed damselfly (Erythromma viridulum) has shifted into the UK since 1999, and may affect resident Odonata via intraguild predation. We asked whether the damselfly’s arrival is associated with a decline in resident Odonata.

3. We harnessed the British Dragonfly Society’s dataset, using records from 49,788 site visits between 2000-2015 to construct dynamic species occupancy models for 17 resident UK Odonata. We estimated the potential effect of E. viridulum presence on the probability that each species would persist at a given site, while controlling for potential effects of climate and recording effort.

4. On average, dragonflies (Anisoptera) persisted more frequently at sites where E. viridulum had established, whilst damselflies (Zygoptera) showed no change in persistence. Nevertheless, two resident damselflies, including E. viridulum’s congener, disappeared more frequently when the range-shifter established.

5. We suggest E. viridulum poses minimal risk to most UK resident Odonata. Rather, E. viridulum may be differentially establishing in areas with good habitat quality, where many species of historically resident Odonata are also found. Therefore, high quality, biodiverse sites may become home to increasing numbers of range-shifters in future. Our approach permits rapid-detection of how range-shifters are integrating into resident biota.

More species live outside their native range than at any point in human history. Yet, there is
little understanding of the geographic regions that will be threatened if these species continue
to spread, nor of whether they will spread. We predict the world’s terrestrial regions to
which 833 naturalised plants, birds, and mammals are most imminently likely to spread, and
investigate what factors have hastened or slowed their spread to date. There is huge potential
for further spread of naturalised birds in North America, mammals in Eastern Europe,
and plants in North America, Eastern Europe, and Australia. Introduction history, dispersal,
and the spatial distribution of suitable areas are more important predictors of species spread
than traits corresponding to habitat usage or biotic interactions. Natural dispersal has driven
spread in birds more than in plants. Whether these taxa continue to spread more widely
depends partially on connectivity of suitable environments. Plants show the clearest invasion
lag, and the putative importance of human transportation indicates opportunities to
slow their spread. Despite strong predictive effects, questions remain, particularly why so
many birds in North America do not occupy climatically suitable areas close to their existing
ranges.

Native biodiversity is threatened by the spread of non-native invasive species. Many studies demonstrate that invasions reduce local biodiversity, but we lack an understanding of how impacts vary across environments at the macroscale. Using ~11,500 vegetation surveys from ecosystems across the United States, we quantified how the relationship between non-native plant cover and native plant diversity varied across different compositions of invading plants (measured by non-native plant richness and evenness) and environmental contexts (measured by productivity and human activity).

Aim
Many species undergo climate niche expansion during naturalisation, in which species spread into climates with which they have not been previously associated. This suggests that species are absent from some climatically suitable areas in their native range, but it is unknown why. We aim to evaluate whether the climate conditions in which expansion occurs inform the causes of niche expansion.
Location
Global
Time period
Contemporary
Major taxa studied
Terrestrial plants
Methods
We compiled native and naturalised occurrence data for 606 terrestrial plant species, and compared their native and naturalised climate niches to detect evidence of climatic niche expansion. Where species show evidence of niche expansion, we used a variety of circular modelling techniques to further investigate whether species are more likely to expand, or expand further, along some climatic axes than others. We also asked, with or without expansion, whether species are more successful at colonising the hottest, coldest, wettest or driest portions of their potential niche.
Results
We find climatic niche expansion in 45% of naturalisations of 606 terrestrial plants. Species predominantly expand into wetter climate than their native niche, somewhat less frequently into drier climate, and only rarely into hotter or colder climate. Species are least likely to naturalise in the hottest or coldest portions of their native climatic niche.
Main conclusions
Our results could suggest that the wetter margins of native niches are limited by biotic interactions, which are relaxed in the naturalised range, evolutionary adaptation to novel precipitation regimes, and/or time lags caused by slow population growth rates in cold and hot conditions. Regardless of the explanation, range margins associated with precipitation might be the least predictable during naturalisation or environmental change.

Aim Understanding the factors that govern species’ geographic ranges is of utmost importance to predict potential range shifts triggered by environmental change. Species' ranges are partially limited by their tolerances to extrinsic environmental conditions such as climate and habitat. However, they are also determined by species’ capacity to disperse, establish new populations, and proliferate, which are in turn dependent on species’ intrinsic life-history traits. So far, the contribution of intrinsic factors driving species’ distributions has been inconclusive, largely because intrinsic and extrinsic factors have not satisfactorily been examined simultaneously. We investigate how geographic ranges of plants are determined by both extrinsic environmental factors and species' intrinsic life-history traits.
Location Europe.
Methods We compiled a database on plant geographic ranges, environmental tolerances and life-history traits that constitutes the largest dataset analysed to date (1276 species). We performed GLMs to test if range size and range filling (the proportion of climatically suitable area a species occupies) are affected by dispersal distance, habitat breadth and 10 life-history traits related to establishment and proliferation.
Results the species’ characteristics that were most linked to range limitations of European plant species were dispersal potential, seed bank persistence and habitat breadth (which together explained ≥30% of deviance in range filling and range size). Specific leaf area, which has been linked to establishment ability, contributed in a smaller way to native range limitations.
Main conclusions Our results can be used to improve estimates of extinction vulnerability under climate change. Species with high dispersal capacity, that can maintain viable seed banks for several years and that can live in an intermediate number of habitats have the least non-climatic limitations on their ranges, and are most likely to shift their geographic ranges under climate change. We suggest that climate-change risk assessments should not focus exclusively on dispersal capacity.#

Information on species’ ecological traits might improve predictions of climate-driven range shifts. However, the usefulness of traits is usually assumed rather than quantified. We present a framework to identify the most informative traits, based on four key range-shift processes: (i) emigration of individuals or propagules away from the natal location, (ii) the distance a species can move, (iii) establishment of self-sustaining populations, and (iv) proliferation following establishment. We propose a framework that categorises traits according to their contribution to range-shift processes. We demonstrate how the framework enables the predictive value of traits to be evaluated empirically, how this categorisation can be used to better understand range shift processes, and illustrate how range shift estimates can be improved.

Key Biodiversity Areas (KBAs) are a cornerstone of 21st century area-based conservation targets. In tropical KBAs, biodiversity is potentially at high risk from climate change, because most species reside within or beneath the canopy, where small increases in temperature can lead to novel climate regimes. We quantify novelty in temperature regimes by modelling hourly temperatures below the forest canopy across tropical KBAs between 1990 and 2019. We find that up to 66% of KBAs with tropical forest are likely to have transitioned to novel temperature regimes. Nevertheless, 34% of KBAs are providing refuge from novelty, 58% of which are not protected. By conducting the first pan-tropical analyses of changes in below-canopy temperatures, we identify KBAs that are acting as climate refugia and should be prioritised as candidates for expansion of the conservation network in response to the post-2020 Global Biodiversity Framework target to conserve 30% of land area by 2030.

Borneo is one of the most species rich regions in the world, but it also has some of the highest rates of deforestation. Much of the remaining unprotected forest is within Indonesian Borneo, but the country’s high rate of deforestation and expansion of industrial concessions threatens those few intact regions. While we know Indonesia has some of the highest national rates of deforestation, this rate is averaged across regions with varying levels of forestry activity. As such, more regional conservation effort would benefit from focused assessment, particularly in areas under active exploitation, so that the consequences of deforestation in the landscape of interest can be addressed.

Borneo’s mammals constitute a rich and varied group of species, many of which are endemic. However, due primarily to anthropogenic impacts, many are now threatened and endangered. Although Bornean mammals have been extensively studied for decades, there are still regions and forest types for which we have limited understanding of the mammal communities. Even within the forests themselves, our knowledge is biased towards terrestrial mammal communities due to our methods of observation. However, tropical forests are vertically complex habitats, supporting numerous arboreal and semi-arboreal species. The expansion of typically terrestrial camera trap survey methods into the canopy is beginning to highlight how our neglect for arboreal observations has biased our understanding of mammal communities in the tropics.

The Rungan Forest Landscape (Rungan) in Indonesian Borneo is a place in need of both localized assessments of deforestation and research into its ecology and mammal community. The Rungan has a large, contiguous forest with regions that are unprotected and regions under active concession development. However, the Rungan’s ecology is poorly understood as little research has been done in the landscape. It also contains Kerangas, a rare and poorly studied type of dry lowland forest for which we have no understanding of the mammal community composition. Peat swamp is the other dominant forest type in the landscape, which is known to support high mammal richness and whose preservation is crucial for climate change mitigation due to their immense peat deposits. Given the rarity of large areas of intact forest in Borneo, the presence of ecologically important species and habitats, and the lack of research there to-date, the Rungan represents an important conservation and research opportunity.

In this thesis I assess the Rungan landscape in two distinct ways: I evaluate the patterns of deforestation and then assess the mammal community in both terrestrial and arboreal space across the habitat types.

I first classify the Rungan’s landcover for 2015 and 2018 to evaluate the change in forest cover. Using these outputs and data on the allocation on industrial concessions in the landscape, I evaluate the patterns of deforestation and the resulting forest spatial attributes across land-uses and forest types. I calculate forest fragmentation and forest cover in 2015 and 2018, and I combine these metrics into ‘forest-continuity’. Species perceive and respond to the same landscape at different spatial scales, so will be variably impacted by deforestation and fragmentation of a landscape. To account for this, I evaluate the landscape’s spatial attributes – fragmentation and forest cover – at three different spatial resolutions. To identify areas of relatively intact forest, I designate a threshold for the degree of fragmentation and amount of forest cover, above which I term ‘high-continuity’.

I assess the mammal community at a study site in the Rungan which is located where two well defined forest types meet – Kerangas and Low Pole (a sub-habitat of peat swamp) – creating a third Transition habitat between them. I use terrestrial and arboreal camera traps to determine the mammal community across habitat types and strata. Using arboreal camera trap surveys is still an emerging method, so here I evaluate the contribution of arboreal cameras to the species richness detected. A common source of sampling error for camera trap data is imperfect detection – when an individual or species is present in the area being sampled but is not detected. Occupancy modelling was developed to account for imperfect detection, enabling more robust comparisons of mammal communities. As such, I use hierarchical multi-species occupancy models to evaluate the mammal metacommunity structure and species-specific occupancy in each habitat type.

From my landcover assessment, I found that the Rungan had a substantially higher rate of deforestation (-7.8%/year) than the Indonesian average (-0.78%/year). Most of the forest loss was in industrial concessions (-8.8%/year) but the rate of deforestation outside of concession areas was also high (-5.3%/year). Although small-scale forestry activity does occur outside of concessions, the disparity between the national rate and that outside of concessions is alarming. Additionally, most deforestation occurred in the Dry lowland forest (containing Kerangas), with minimal losses in Peat swamp. This difference was largely due to concessions being predominantly distributed in Dry lowland while some of the Peat swamp forest has been put under a moratorium on development. From the assessment of fragmentation and forest cover, I found a reduction in amount of high-continuity forest area and a widening of the gaps between adjacent high-continuity regions. The region that has conservation potential is the high-continuity forest outside of concessions. In 2018, this represented 522 – 628 km2, depending on the spatial resolution of analysis. However, Peat swamp is disproportionately represented in that high-continuity forest outside of concessions, and that which does occur in Dry lowland is itself divided around the landscape.

I found high mammal species richness in the study site (47 species), with 43 species detected in Kerangas and 29 species detected in Low Pole. Including arboreal camera traps significantly increased the number of species detected, more than expected by doubling the terrestrial effort alone. The arboreal camera traps provided valuable information beyond just the number of species, such as detections of threatened species, increased understanding of habitat use, and the detection of two species whose current known geographic distributions exclude Central Kalimantan. The outputs from the occupancy models showed that mammal richness and species-specific occupancy probability tended to be higher in Kerangas and Transition compared to Low Pole. This was true for both terrestrial and arboreal communities. I also found that some species detected by both terrestrial and arboreal surveys differed in their mean occupancy values between strata in the same habitat.

My research highlights the importance of regional-scale analysis of deforestation patterns and the importance of comprehensive surveys of both terrestrial and arboreal space when studying mammal communities. I illustrate that national averages are not necessarily representative of the patterns of forest loss in unprotected and actively exploited landscapes. Regional-scale analysis should be done to better understand patterns and drivers of deforestation, and to identify areas of conservation priority. The impacts of deforestation are species-specific though, so it is also important to account for variability in species’ perceptions of the landscape. My research also shows that combing arboreal and terrestrial camera trap surveys produces a more accurate representation of the mammal community than terrestrial surveys alone. This leads to more accurate community- and species- level assessments, which is essential for conservation and impact assessments. As the first assessment of the mammal community in Kerangas, I have also shown that it supports a rich mammal community and is of high ecological and conservation value.

Abstract
. Tropical forest biodiversity is potentially at high risk from climate change, but most species reside within or beneath the canopy, where they are buffered from extreme temperatures, implying that forest canopies may reduce the severity of warming impacts. Using a mechanistic microclimate model, we quantify hourly below-canopy climate conditions of 300,000 tropical forest locations globally between 1990–2019. We show that while temperature extremes are buffered below canopy, recent small increases in beneath-canopy temperature (<1ºC) have led to highly novel temperature regimes across most of the tropics. This is the case even within ecologically unfragmented areas, suggesting that tropical forests are sensitive to climate change. However, across the globe, some forest areas have experienced low climate novelty and thus serve as. important climate refugia. These areas require urgent protection and restoration. By conducting the first pan-tropical analyses of changes in below-canopy climatic conditions, we challenge the prevailing notion that tropical forest canopies reduce the severity of climate change impacts.

Species distribution models (SDMs) have emerged as a powerful research tool for predicting the impact of climate change on global biodiversity and are increasingly being used to guide international and local decision-making for conservation. However, the accuracy of these models is limited by their reliance on seasonally aggregated climate data derived from weather stations, which fail to reflect conditions experienced by organisms in nature. This is because climate conditions vary in multiple dimensions: geographical space, vertical space, and through time. In this thesis, I explore what this means for predicting the impact of climate change on global biodiversity. I demonstrate that the conclusions reached about where, and which species are most threatened by climate change is fundamentally altered when the discrepancy between standard climate data and conditions experienced by species is considered. In Chapter 2, I show that global diversification has, in part, been driven by spatiotemporal variation in climate, such that the most diverse regions have historically experienced relatively stable conditions and are thus more sensitive to changes that do occur. In Chapter 3, I show that the choice of near-ground or free-air temperatures to fit SDMs significantly influences which places are perceived as most vulnerable to climatic changes. In Chapters 4 and 5, I investigate the temporal and vertical dimensions of climate change and demonstrate that even modest changes can result in widespread and pervasive novel conditions across the tropics. Finally, in Chapter 6, I incorporate spatiotemporal climate gradients into SDMs to investigate whether recent climate changes have resulted in declines of climate suitability and species richness for neotropical bird species. I conclude by emphasising the need to realistically capture the conditions experienced by organisms when predicting how they are responding to climate change. My thesis demonstrates the importance of accurately capturing multi-dimensional climate gradients and considering how they are relevant to organisms when predicting the impact of climate change on global biodiversity. By doing so, predictive modelling can better inform conservation strategies to protect the most vulnerable species and regions.

Abstract


The global redistribution of species due to climate change and other anthropogenic causes is driving novel human–wildlife interactions with complex consequences. On the one hand, range‐shifting species could disrupt recipient ecosystems. On the other hand, these species may be contracting in their historic range, contributing to loss of biodiversity there. Given that arriving range‐shifting species could also perhaps have positive effects on recipient ecosystems, there is [in principle] a net benefit equation to be calculated. Thus, public opinion on these species may be divided and they may present a unique challenge to wildlife management.

We surveyed the opinion of wildlife recorders about the establishment and management of eight birds and eight insects whose ranges have recently shifted into the United Kingdom. We asked whether respondents' attitudes were explained by the species' or respondents' characteristics, and whether or not climate change was emphasised as a cause of range‐shift. We also conducted qualitative analysis of the recorders' text responses to contextualise these results.

Attitudes to range‐shifting species were mostly positive but were more ambivalent for less familiar taxa and for insects compared with birds. Respondents were strongly opposed to eradicating or controlling new range‐shifters, and to management aimed to increase their numbers. Whether climate change was presented as the cause of range‐shifts did not affect attitudes, likely because respondents assumed climate change was the driver regardless.

These findings suggest that it will be difficult to generate support for active management to support or hinder species' redistribution, particularly for invertebrate or overlooked species among wildlife recorders. However, the positive attitudes suggest that on the whole range‐shifting species are viewed sympathetically. Engaging with wildlife recorders may represent an opportunity to garner support for conservation actions which will benefit both currently native and arriving species, such as improvements to habitat quality and connectivity.

Read the free Plain Language Summary for this article on the Journal blog.

The fall armyworm (FAW), Spodoptera frugiperda (JE Smith, 1797), is a serious
pest of several crops, particularly maize and other cereals. It has long been known as a
pest in the Americas and has invaded most of Africa and parts of the Middle East, Asia,
and Australia in the last six years. Its new status as an invasive species causing serious
damage in many regions worldwide has highlighted the need for better understanding and
has generated much research. In this article, we provide a comprehensive review of FAW
covering its (i) taxonomy, biology, ecology, genomics, and microbiome, (ii) worldwide
status and geographic spread, (iii) potential for geographic expansion and quarantine
measures in place, and (iv) management including monitoring, sampling, forecasting,
biological control, biopesticides, agroecological strategies, chemical control, insecticide
resistance, effects of insecticides on natural enemies, as well as conventional and
transgenic resistant cultivars. We conclude with recommendations for research to
enhance the sustainable management of FAW in invaded regions.

Abstract
. The expectation that places with suitable climate will lie outside the current range of many species has shaped 21st century conservation policy and led to predictions of numerous extinctions. We show that the magnitude of range shifts is often overestimated because the climate data typically used do not reflect the microclimatic conditions that many organisms experience. We model the historic (1977–1995) distributions of 302 plant taxa using both macro- and microclimate data and project these distributions forward to present day (2002–2020). Whereas macroclimate models predicted major range shifts (mean: 9.2 km per decade), microclimate models predicted localised shifts into favourable microclimate (mean: 88 m per decade) that more closely match observed patterns of establishment and extinction. In consequence, improving protecting of refugial populations within species’ existing geographic range is likely to be more effective for many species than assisted translocations and overhaul of protected area networks.

AbstractInvasive species have historically been a problem derived from global trade and transport. To aid in the control and management of these species, species distribution models (SDMs) have been used to help predict possible areas of expansion. Our focal organism, the African Armyworm (AAW), has historically been known as an important pest species in Africa, occurring at high larval densities and causing outbreaks that can cause enormous economic damage to staple crops. The goal of this study is to map the AAW’s present and potential distribution in three future scenarios for the region, and the potential global distribution if the species were to invade other territories, using 40 years of data on more than 700 larval outbreak reports from Kenya and Tanzania. The present distribution in East Africa coincides with its previously known distribution, as well as other areas of grassland and cropland, which are the host plants for this species. The different future climatic scenarios show broadly similar potential distributions in East Africa to the present day. The predicted global distribution shows areas where the AAW has already been reported, but also shows many potential areas in the Americas where, if transported, environmental conditions are suitable for AAW to thrive and where it could become an invasive species.

Tropical rainforests are one of the most diverse biomes on the planet and provide vital ecological services, including climate regulation through carbon sequestration. Borneo has incredibly high biodiversity that is under threat due to anthropogenic pressure, which leads to widespread deforestation due to mining, logging and the conversion of land to plantations. Protecting this biodiversity, as well as documenting and monitoring it to inform conservation strategies, are of great priority. This study centres on the unprotected Rungan Forest Landscape in Central Kalimantan Province, Indonesian Borneo. This lowland forest is a mosaic of different habitats, including peat swamp forests (Low Pole), the sandy soil heath forest (Kerangas) and a transitional forest between the two (Mixed Swamp). Peatlands are relatively well studied and are known to be a key habitat for critically endangered species such as orangutans (Pongo pygmaeus) as well as storing large quantities of carbon. Lowland Kerangas habitats, on the other hand are less well studied and, unlike peat forest, are currently not represented in any protected areas, despite its potential to harbour. a rich and unique biodiversity. High heterogeneity in the Rungan landscape is hypothesised to allow it to support higher biodiversity than expected from peat swamp or Kerangas by itself, due to habitat complementarity, but this has not yet been tested. Here, I investigate this by studying spatial and temporal variation in the community of frugivorous Lepidoptera and their fruit resources. Using ground fruit surveys and baited Lepidoptera traps, 17 plots of three different habitats (Kerangas, Mixed Swamp and Low Pole) were surveyed monthly for five consecutive months between April and August 2019. In chapter 2 I use this data to test whether there are significant differences in frugivorous Lepidoptera abundance, richness and diversity between the habitat types and months and whether this correlates with variation in fruit abundance, richness and diversity. I show that there are significant differences in: fruit abundance and diversity; butterfly abundance; and moth abundance and species richness. I also show that there was no correlation between Lepidoptera abundance, richness and diversity with fruit abundance, richness and diversity. In chapter 3 I use the same data set to test whether species composition of Lepidoptera and fruit differs between the habitats. Secondly, I test whether similarity in Lepidoptera species composition among sample sites correlates with similarity in fruit species composition among sample sites. Thirdly, I test for spatial correlation in species composition regardless of habitat. I show that species composition of Lepidoptera and fruit differs between the habitats and has a correlation between them. Finally I show there is spatial correlation within the study. Temporal variation in abundance, richness and diversity over the five study months indicates that further study is required to identify the drivers of this, for example seasonality, which may lead to asynchrony in resource availability among the habitats, providing a further source of complementarity. Further, it is noted that among Lepidoptera, the results are not always consistent between moths and butterflies and this raises questions about assumptions underlaying the use of ‘indicator taxa’, such as butterflies. Using this study as a baseline for community structures across several habitats and months, future surveys will be able to quickly detect any changes due to any external pressures like mining or fragmentation due to logging. Being able to quickly identify the effect of such threats on community structures can help guide protection measures. Together, the results indicate that the heterogeneous landscape could be leading to greater overall species diversity of the region, and therefore the principal of habitat complementarity stresses that all the habitats within the mosaic of the Rungan landscape should be protected.

In the past 50 years, around 30% of Borneo has been deforested. Despite an increase in conservation and research effort, taxonomic and geographic biases mean vast areas of Borneo’s tropical forests remain undescribed and unprotected.
This study provides the first survey of the non-volant, small mammal community inhabiting the Rungan Landscape, Borneo. Data from four months of Capture-mark- recapture surveys in three distinct habitat types has revealed a small mammal community of 12 species from 3 different orders. A range expansion of Maxomys ochraceiventer, plus the potential discovery of a new Maxomys species highlights the lack of knowledge of this taxon and how its species are distributed across Borneo. Morphological discrepancies found between observed and the expected morphology described in existing literature demonstrates the issues of generalising data across regions. Significant differences were found in small mammal composition and richness across habitat types which provides supporting evidence for the habitat complementarity principle and habitat heterogeneity hypothesis in the Rungan Landscape. I found that within this forest mosaic, low pole forest has the highest number of specialist species, endemics and the highest overall species richness which contradicts previous beliefs that peat-swamp forests have low-levels of biodiversity. Findings from this study have increased our ecological knowledge about the small mammal species inhabiting this region and demonstrated the positive effect of landscape heterogeneity on biodiversity. With information on the distribution and diversity of species widely used as a basis for setting conservation priorities, this data will increase the efficacy of proposed conservation efforts and highlight the importance of protecting this landscape to protect this small mammal community as well as the overall biodiversity of this landscape.

CONTEXT:
Species distributions are rapidly altering in the 21st century. Climate change and other anthropogenic effects threaten historic ranges but also open up new regions for expansion. Distributional changes will create novel biotic interactions that may significantly affect ecosystems, and humanity, both positively and negatively. Range-shifters create conservation conundrums, which may require us to balance the conservation value of newly arriving species against their impacts on existing biodiversity. To tackle these conundrums we will have to understand why and how species are moving, be able to make predictions of what potential effects may be felt in the new range and recognise how species are perceived when they arrive there.
APPROACHES:
I explore three aspects of species redistribution: processes, consequences, and perceptions. To better understand the redistribution process, I investigate the importance of climate, habitat, and proximity to source populations in predicting 14 range-shifting birds’ distributions in Britain. I explore consequences by estimating effects of a range-shifting damselfly on UK Odonata with dynamic multispecies occupancy (DMSO) models. Finally, I explore perceptions by surveying UK wildlife recorders’ attitudes towards range-shifting species and their management.
RESULTS:
I found that climate did not predict most analysed range-shifters’ British distributions effectively. Despite being comparatively better, neither habitat nor distance from European breeding sites were good absolute predictors. Counter-intuitively, our DMSO model predicted that 15/17 resident dragonflies were more likely to persist at sites where the range-shifting damselfly established. Survey responses revealed that recorders opposed efforts to either control or support range-shifters, instead favouring non-intervention.
IMPLICATIONS:
The poor predictive power of climate suggests that we should explicitly study the full potential suite of range-shift processes, including biotic interactions and constraints on species movement. The absence of a negative association between the range-shifting damselfly and most Odonata species should be welcomed, but cautiously as other factors (e.g. habitat) may confound the range-shifters’ effect. Recorders’ averseness to interventions suggests that ecological research focused on the feasibility of both assisted colonisation and range-shifter threat should also seek to understand social contexts for successful conservation. Integrating these findings, I argue that we should use rapidly growing ecological datasets to not just detect but to test and refine theories of range-shift. Future model refinement alongside fuller understanding of stakeholder perspectives will help enable equitable – and ecologically beneficial – range-shift management.

Climate change is regarded as a primary threat to global biodiversity. One avenue in which climate change is influencing survival is through the minimisation of the efficacy of anti-predator defences. Background matching camouflage is an anti-predator defence whereby an organism remains undetectable even when in plain sight. Within seasonal coat colour species, species which undergo a colour changing biannual moult thought to provide anti-predator colouration in their seasonally variable environment, the occurrence of camouflage mismatch is beginning to be recorded. The primary subject of this camouflage mismatch research has been the snowshoe hare (Lepus americanus). However, whilst this mismatch is being observed in nature and is impacting survival rate in snowshoe hares and other seasonal coat colour species, no research as of yet has examined whether these seasonal moults provide background-matching camouflage. In addition, no previous research has examined the impact of camouflage mismatch on detectability from an ecologically relevant visual system, such as the most common mammalian visual system: dichromatism. Within this thesis, both of these gaps in knowledge are explored through computer detection experiments and eye movement analysis in humans.

In chapter two, I investigate the impact of predator visual system, camouflage efficacy, background complexity, coat colour, and seasonal background type on the detection rate of snowshoe hares. Participants were displayed 15 randomly generated images of snowshoe hares on a natural landscape and located the snowshoe hares as quickly as possible. Snowshoe hares were detected more rapidly when their camouflage was ineffective, both in colour and brightness. In addition, more complex backgrounds resulted in longer search times. Although visual systems did not differ in overall detection times, simulated dichromatic vision resulted in longer search times for brightness camouflaged snowshoe hares. Within chapter three, I build upon the findings of chapter two, utilising eye-tracking equipment to examine participant visual attention and search mechanisms whilst locating snowshoe hares. I found that simulated dichromatic and trichromatic visual systems differ dramatically in the mechanisms used within the detection and discrimination of a camouflaged target. I also found that camouflage efficacy and background complexity function primarily as a method to reduce detectability, but do not influence the discriminability of a snowshoe hare from its background.

This thesis provides support to previous research indicating that climate change will have a significant negative impact on the efficacy of seasonal coat colour camouflage and thus survival. The effects of this are already being recorded in the wild, with mismatched snowshoe hares experiencing elevated predation rates. This thesis supports that the primary reason for the increased predation is ineffective background-matching camouflage. Many aspects of camouflage and prey detection are explored within this thesis which are yet to be tested in seasonal coat colour species in the wild. In particular, how background complexity influences detectability, and the importance of considering an ecologically relevant predator visual system when examining camouflage. Overall, this thesis indicates that as the camouflage efficacy of seasonal coat colour species further decreases due to climate change, detectability, and thus predation risk, will increase.

Abstract
. Crops worldwide are simultaneously affected by weeds, which reduce yield, and by climate change, which can negatively or positively affect both crop and weed species. While the individual effects of environmental change and of weeds on crop yield have been assessed, the combined effects have not been broadly characterized. To explore the simultaneous impacts of weeds with changes in climate-related environmental conditions on future food production, we conducted a meta-analysis of 171 observations measuring the individual and combined effects of weeds and elevated CO2, drought or warming on 23 crop species. The combined effect of weeds and environmental change tended to be additive. On average, weeds reduced crop yield by 28%, a value that was not significantly different from the simultaneous effect of weeds and environmental change (27%), due to increased variability when acting together. The negative effect of weeds on crop yield was mitigated by elevated CO2 and warming, but added to the negative effect of drought. The impact of weeds with environmental change was also dependent on the photosynthetic pathway of the weed/crop pair and on crop identity. Native and non-native weeds had similarly negative effects on yield, with or without environmental change. Weed impact with environmental change was also independent of whether the crop was infested with a single or multiple weed species. Since weed impacts remain negative under environmental change, our results highlight the need to evaluate the efficacy of different weed management practices under climate change. Understanding that the effects of environmental change and weeds are, on average, additive brings us closer to developing useful forecasts of future crop performance.

As climate change progresses, the ranges of many species will begin to shift. Which species will have their ranges shifted and where, will have major consequences for conservation, habitat management, agriculture, and human health. This thesis furthers our understanding of the processes that limit and facilitate range expansion by investigating the appearance of the hermit crab Clibanarius erythropus to the southwest United Kingdom (UK). Evidence suggests that C. erythropus arrived in the southwest UK via the species’ pelagic larvae drifting on ocean currents. The Mer d'Iroise, the historical limit of C. erythropus’ range, is a biological transition zone where the warm-water species found in the Bay of Biscay transition to the colder-water species of Northern Europe. Consequently, C. erythropus may be one of the first of many species whose range will expand to the southwest UK in the future. In chapter one, we study the phylogeographic structure of C. erythropus across its historic and newly established range. C. erythropus is a rare example of panmixia in the European seascape, indicating that populations of C. erythropus are interconnected and that the species has overcome most barriers to gene flow seen in other intertidal species. Panmixia suggests that the range of C. erythropus can readily shift with environmental change. In chapter two, we investigate the oceanographic processes that facilitated the transportation of C. erythropus to the UK. Using a hydrodynamic model, we simulate the dispersal of C. erythropus larvae in the English Channel over a number of years. Simulations suggest the larvae of C. erythropus arrived in 2014, originated from North Brittany, experienced a mean temperature of around 16 °C, and took longer than 20 days to be transported across the English Channel. Our results suggest that the transportation of larvae from Brittany to the southwest UK is rare and driven by the stochasticity of ocean currents which could limit the ability of many species to adequately shift their range to the UK with climate change.

AbstractAimClimate change impacts forest functioning and services through two inter‐related effects. First, it impacts tree growth, with effects, for example, on biomass production. Second, climate change also reshuffles community composition, with further effects on forest functioning. However, the relative importance of these two effects has rarely been studied. Here, we developed a new modelling approach to investigate these relative importances for forest productivity.LocationEleven forest sites in central Europe.Time periodHistorical (1990) and end‐of‐21st‐century climate‐like conditions. We simulated 2,000 years of forest dynamics for each set of conditions.Major taxa studiedTwenty‐five common tree species in European temperate forests.MethodsWe coupled species distribution models and a forest succession model, working at complementary spatial and temporal scales, to simulate the climatic filtering that shapes potential tree species pools, the biotic filtering that shapes realized communities and the functioning of these realized communities in the long‐term.ResultsUnder an average temperature increase (relative to 1901–1990) of between 1.5 and 1.7 °C, changes in simulated forest productivity were caused mostly by changes in the growth of persisting tree species. With an average temperature increase of 3.6–4.0 °C, changes in simulated productivity at sites that currently have a mild climate were again caused predominantly by changes in tree species growth. However, at the warmest and coldest sites, changes in productivity were related mostly to shifts in species composition. In general, at the coldest sites, forest productivity is likely to be enhanced by climate change, whereas at the warmest sites the productivity might increase or decrease depending on the future precipitation regime.Main conclusionsA combination of two complementary modelling approaches that address questions at the interface between biogeography, community ecology and ecosystem functioning, reveals that climate change‐driven community reshuffling in the long term might be crucially important for ecosystem functioning.

BACKGROUND: the fall armyworm (FAW), an invasive pest from the Americas, is rapidly spreading through the Old World, and has recently invaded the Indochinese Peninsula and southern China. In the Americas, FAW migrates from winter-breeding areas in the south into summer-breeding areas throughout North America where it is a major pest of corn. Asian populations are also likely to evolve migrations into the corn-producing regions of eastern China, where they will pose a serious threat to food security. RESULTS: to evaluate the invasion risk in eastern China, the rate of expansion and future migratory range was modelled by a trajectory simulation approach, combined with flight behavior and meteorological data. Our results predict that FAW will migrate from its new year-round breeding regions into the two main corn-producing regions of eastern China (Huang-Huai-Hai Summer Corn and Northeast Spring Corn Regions), via two pathways. The western pathway originates in Myanmar and Yunnan, and FAW will take four migration steps (i.e. four generations) to reach the Huang-Huai-Hai Region by July. Migration along the eastern pathway from Indochina and southern China progresses faster, with FAW reaching the Huang-Huai-Hai Region in three steps by June and reaching the Northeast Spring Region in July. CONCLUSION: Our results indicate that there is a high risk that FAW will invade the major corn-producing areas of eastern China via two migration pathways, and cause significant impacts to agricultural productivity. Information on migration pathways and timings can be used to inform integrated pest management strategies for this emerging pest. © 2019 Society of Chemical Industry.

AbstractMany analyses of biological responses to climate rely on gridded climate data derived from weather stations, which differ from the conditions experienced by organisms in at least two respects. First, the microclimate recorded by a weather station is often quite different to that near the ground surface, where many organisms live. Second, the temporal and spatial resolutions of gridded climate datasets derived from weather stations are often too coarse to capture the conditions experienced by organisms. Temporally and spatially coarse data have clear benefits in terms of reduced model size and complexity, but here we argue that coarse‐grained data introduce errors that, in biological studies, are too often ignored. However, in contrast to common perception, these errors are not necessarily caused directly by a spatial mismatch between the size of organisms and the scale at which climate data are collected. Rather, errors and biases are primarily due to (a) systematic discrepancies between the climate used in analysis and that experienced by organisms under study; and (b) the non‐linearity of most biological responses in combination with differences in climate variance between locations and time periods for which models are fitted and those for which projections are made. We discuss when exactly problems of scale can be expected to arise and highlight the potential to circumvent these by spatially and temporally down‐scaling climate. We also suggest ways in which adjustments to deal with issues of scale could be made without the need to run high‐resolution models over wide extents.

Abstract
Background
In 2016, the range of the hermit crab Clibanarius erythropus expanded to South West Britain for the second time. C. erythropus primarily lives in the Mediterranean and the Atlantic coast of Europe from the Bay of Biscay to Morocco. The species has now been recorded on both the north and south coast of the South West peninsula of the UK from Newtrain Bay, on the north coast of Cornwall, to Wembury, on the south coast of Devon. It is unknown if the crab’s reappearance in the UK has been caused by a one-off colonisation event or by a continued influx of larvae.

Results
The population in the UK is made up of individual within a narrow size bracket, indicating a single colonisation event took place, and that the population is an ageing one. However, we also report the highest latitude recording of a gravid individual for the species.

Conclusion
A lack of gravid individuals was suggested to be why the species was unable to sustain its presence in the UK following a previous colonisation in 1960. This discovery hints that rising water temperatures may allow C. erythropus and other warm-water species to expand and sustain themselves in the UK. We also found crossover in shell utilisation between C. erythropus and the native hermit crab Pagurus bernhardus, suggesting that competition might occur between the two species.

The study of species’ range margins has a long history of academic interest, but is of particular relevance today due to its applications in modelling species range shifts induced by climate change, and predicting the spread of invasive species. Climate has long been assumed to structure species’ ranges over broad scales, but this consensus has recently been challenged by work on non-climatic factors, such as dispersal, biotic interactions and gene flow. It remains unclear how and where non-climatic factors can structure species’ ranges, and to what extent species’ ranges will consistently match sets of climatic conditions.
In this thesis I investigate what can lead to a species underfilling its climatic niche (when a species fails to colonise all climatically suitable areas), or expanding its climatic niche (when a species is able to colonise new types of climate). I find evidence that several non-climatic factors can slow or prevent non-native species colonising all climatically suitable areas in their naturalised regions, including dispersal, fragmentation of climatically suitable areas and the area of introduction. I also find that species will readily spread into new precipitation regimes with which they have not been previously associated. This suggests that species ranges can be constrained by non-climatic factors in the wettest part of their native range, and these constraints are frequently lifted in their naturalised range. I find evidence that species range limits set by temperature, in particular temperature maxima and minima, are more conserved and species will rarely expand into new thermal regimes. I also find evidence that species have different phenotypic responses to temperature across their range. Together these results indicate that a species’ current range frequently does not indicate its overall climatic tolerance, particularly in relation to precipitation, hence predictions that rely on associations between occurrence and environmental variables will frequently be flawed. Future work should consider a systematic way of detecting and including non-climatic factors that constrain the edges of species’ ranges.

This thesis brings together information from three different techniques to provide novel information on the ecology of range-shifting gilthead seabream Sparus aurata in the Northeast Atlantic. My chapters take a systematic look at the ecology of S. aurata around the UK, to help explain the drivers that are facilitating the northwards range-shift. First, I use species distribution modelling to investigate the relative importance of temperature on the current distribution of S. aurata, and how it is likely to affect the species range in the future. I find that northern populations of S. aurata appear to be occupying a very different thermal niche to those in the native range, indicating that either a niche shift has occurred, or that northern populations consist primarily of non-reproducing adults. Although this distinction has important implications for successful management of the species, I also find that climate change is likely to result in a further northward shift by 2050. This climate-driven shift is likely to facilitate reproducing populations in the English Channel and the Celtic Sea, assuming that suitable nursery areas are available. Second, I use otolith microchemistry to identify whether multiple sources are contributing to S. aurata populations in the English Channel. Using a multi-element approach, I find evidence for three sources contributing to S. aurata populations in the Channel that have shared otolith chemistry, and that these are temporally stable. These sources could relate to environments that are either spatially or temporally-discrete. I also find that, although there appears to be some mixing after spawning, the three different sources do not contribute equally to populations in the Channel. This mixing could occur during larval dispersal or subsequent adult movement. The multi-element approach allows speculation as to where these sources could be and provides a basis for future research into identifying specific spawning locations. Finally, I use stable isotopes to investigate the potential consequences of increasing S. aurata populations on European seabass Dicentrarchus labrax, by examining the potential for resource competition between juveniles. I find that although both species appear to be feeding on similar prey, they also appear to have different realised niches within the study system. This apparent resource partitioning could indicate a negative competitive effect or a positive indirect effect through indirect mutualism. To my knowledge, this is the first in-depth study of S. aurata in UK waters. Therefore, this thesis provides useful information that can help inform future management measures and conservation of this target species.

To predict the threat of biological invasions to native species, it is critical that we understand how increasing abundance of invasive alien species (IAS) affects native populations and communities. The form of this relationship across taxa and ecosystems is unknown, but is expected to depend strongly on the trophic position of the IAS relative to the native species. Using a global metaanalysis based on 1,258 empirical studies presented in 201 scientific publications, we assessed the shape, direction, and strength of native responses to increasing invader abundance. We also tested how native responses varied with relative trophic position and for responses at the population vs. community levels. As IAS abundance increased, native populations declined nonlinearly by 20%, on average, and community metrics declined linearly by 25%. When at higher trophic levels, invaders tended to cause a strong, nonlinear decline in native populations and communities, with the greatest impacts occurring at low invader abundance. In contrast, invaders at the same trophic level tended to cause a linear decline in native populations and communities, while invaders at lower trophic levels had no consistent impacts. At the community level, increasing invader abundance had significantly larger effects on species evenness and diversity than on species richness. Our results show that native responses to invasion depend critically on invasive species' abundance and trophic position. Further, these general abundance-impact relationships reveal how IAS impacts are likely to develop during the invasion process and when to best manage them.

Demand for models in biodiversity assessments is rising, but which models are adequate for the task? We propose a set of best-practice standards and detailed guidelines enabling scoring of studies based on species distribution models for use in biodiversity assessments. We reviewed and scored 400 modeling studies over the past 20 years using the proposed standards and guidelines. We detected low model adequacy overall, but with a marked tendency of improvement over time in model building and, to a lesser degree, in biological data and model evaluation. We argue that implementation of agreed-upon standards for models in biodiversity assessments would promote transparency and repeatability, eventually leading to higher quality of the models and the inferences used in assessments. We encourage broad community participation toward the expansion and ongoing development of the proposed standards and guidelines.

The number of alien plants escaping from cultivation into native ecosystems is increasing steadily. We provide an overview of the historical, contemporary and potential future roles of ornamental horticulture in plant invasions. We show that currently at least 75% and 93% of the global naturalised alien flora is grown in domestic and botanical gardens, respectively. Species grown in gardens also have a larger naturalised range than those that are not. After the Middle Ages, particularly in the 18th and 19th centuries, a global trade network in plants emerged. Since then, cultivated alien species also started to appear in the wild more frequently than non-cultivated aliens globally, particularly during the 19th century. Horticulture still plays a prominent role in current plant introduction, and the monetary value of live-plant imports in different parts of the world is steadily increasing. Historically, botanical gardens - an important component of horticulture - played a major role in displaying, cultivating and distributing new plant discoveries. While the role of botanical gardens in the horticultural supply chain has declined, they are still a significant link, with one-third of institutions involved in retail-plant sales and horticultural research. However, botanical gardens have also become more dependent on commercial nurseries as plant sources, particularly in North America. Plants selected for ornamental purposes are not a random selection of the global flora, and some of the plant characteristics promoted through horticulture, such as fast growth, also promote invasion. Efforts to breed non-invasive plant cultivars are still rare. Socio-economical, technological, and environmental changes will lead to novel patterns of plant introductions and invasion opportunities for the species that are already cultivated. We describe the role that horticulture could play in mediating these changes. We identify current research challenges, and call for more research efforts on the past and current role of horticulture in plant invasions. This is required to develop science-based regulatory frameworks to prevent further plant invasions.

Aim: Our understanding of potential ranges for native and non-native species is often based on their current geographic distributions. Non-native species have had less time than co-occurring native species to expand their ranges following introduction, so non-native ranges may under-represent suitable conditions. Therefore it is often assumed that species distribution models will predict disproportionately smaller potential ranges for non-natives than natives. We compare the distributions of native, endemic, alien and invasive plants to determine how the different range attributes of these groups might influence ecological forecasting. Location: Continental USA. Methods: We compared the geographic ranges of 13,575 plant species (9402 native, 2397 endemic, 1201 alien and 755 invasive) using (1) US only and (2) global distribution data from herbarium records. We calculated US longitudinal and latitudinal range extents as potential indicators of range-limiting factors, modelled potential range based on climate using principal components analysis, and calculated occupancy of potential ranges (range infilling). Results: Contrary to expectations, modelled potential ranges were significantly larger for non-natives than natives, even for species with few occurrences. Distributions of native species, not invasive species, appeared strongly limited longitudinally. However, invasive plants occupied substantially less area within their climatically suitable ranges than native plants (lower range infilling). Main conclusions: Invasive plant distributions were consistently broader, both climatically and geographically, than comparable native species. This suggests that invasive plant distribution models at regional scales are not underpredicting potential ranges relative to models for native species. In contrast, the comparatively limited longitudinal ranges of native species suggest a high degree of non-climatic limitation, which is likely to cause distribution models to underpredict the potential ranges of native species. Invasive plants have not achieved the degree of range infilling expected relative to natives. Thus, plants introduced to the US still have plenty of space to invade.

Aim: Correlative models that forecast extinction risk from climate change and invasion risks following species introductions, depend on the assumption that species’ current distributions reflect their climate tolerances (‘climatic equilibrium’). This assumption has rarely been tested with independent distribution data, and studies that have done so have focused on species that are widespread or weedy in their native range. We use independent data to test climatic equilibrium for a broadly representative group of species, and ask whether there are any general indicators that can be used to identify when equilibrium occurs.

Location: Europe and contiguous USA.

Methods: We contrasted the climate conditions occupied by 51 plant species in their native (European) and naturalized (USA) distributions by applying kernel smoothers to species’ occurrence densities. We asked whether species had naturalized in climate conditions that differ from their native ranges, suggesting climatic disequilibrium in the native range, and whether characteristics of species’ native distributions correspond with climatic equilibrium.

Results: a large proportion of species’ naturalized distributions occurred outside the climatic conditions occupied in their native ranges: for 22 species, the majority of their naturalized ranges fell outside their native climate conditions. Our analyses revealed large areas in Europe that species do not occupy, but which match climatic conditions occupied in the USA, suggesting a high degree of climatic disequilibrium in the native range. Disequilibrium was most severe for species with native ranges that are small and occupy a narrow range of climatic conditions.

Main conclusions: Our results demonstrate that the direct effects of climate on species distributions have been widely overestimated, and that previous large-scale validations of the equilibrium assumption using species’ native and naturalized distributions are not generally applicable. Non-climatic range limitations are likely to be the norm, rather than the exception, and pose added risks for species under climate change.

As the main witnesses of the ecological and economic impacts of invasions on ecosystems around the world, ecologists seek to provide the relevant science that informs managers about the potential for invasion of specific organisms in their region(s) of interest. Yet, the assorted literature that could inform such forecasts is rarely integrated to do so, and further, the diverse nature of the data available complicates synthesis and quantitative prediction. Here we present a set of analytical tools for synthesizing different levels of distributional and/or demographic data to produce meaningful assessments of invasion potential that can guide management at multiple phases of ongoing invasions, from dispersal to colonization to proliferation. We illustrate the utility of data-synthesis and data-model assimilation approaches with case studies of three well-known invasive species—a vine, a marine mussel, and a freshwater crayfish—under current and projected future climatic conditions. Results from the integrated assessments reflect the complexity of the invasion process and show that the most relevant climatic variables can have contrasting effects or operate at different intensities across habitat types. As a consequence, for two of the study species climate trends will increase the likelihood of invasion in some habitats and decrease it in others. Our results identified and quantified both bottlenecks and windows of opportunity for invasion, mainly related to the role of human uses of the landscape or to disruption of the flow of resources. The approach we describe has a high potential to enhance model realism, explanatory insight, and predictive capability, generating information that can inform management decisions and optimize phase-specific prevention and control efforts for a wide range of biological invasions.

Geographical range dynamics are driven by the joint effects of abiotic factors, human ecosystem modifications, biotic interactions and the intrinsic organismal responses to these. However, the relative contribution of each component remains largely unknown. Here, we compare the contribution of life-history attributes, broad-scale gradients in climate and geographical context of species’ historical ranges, as predictors of recent changes in area of occupancy for 116 terrestrial British breeding birds (74 contractors, 42 expanders) between the early 1970s and late 1990s. Regional threat classifications demonstrated that the species of highest conservation concern showed both the largest contractions and the smallest expansions. Species responded differently to climate depending on geographical distribution—northern species changed their area of occupancy (expansion or contraction) more in warmer and drier regions, whereas southern species changed more in colder and wetter environments. Species with slow life history (larger body size) tended to have a lower probability of changing their area of occupancy than species with faster life history, whereas species with greater natal dispersal capacity resisted contraction and, counterintuitively, expansion. Higher geographical fragmentation of species' range also increased expansion probability, possibly indicating a release from a previously limiting condition, for example through agricultural abandonment since the 1970s. After accounting statistically for the complexity and nonlinearity of the data, our results demonstrate two key aspects of changing area of occupancy for British birds: (i) climate is the dominant driver of change, but direction of effect depends on geographical context, and (ii) all of our predictors generally had a similar effect regardless of the direction of the change (contraction versus expansion). Although we caution applying results from Britain's highly modified and well-studied bird community to other biogeographic regions, our results do indicate that a species' propensity to change area of occupancy over decadal scales can be explained partially by a combination of simple allometric predictors of life-history pace, average climate conditions and geographical context.

The current distributions of species are often assumed to correspond with the total set of environmental conditions under which species can persist. When this assumption is incorrect, extinction risk estimated from species distribution models can be misleading. The degree to which species can tolerate or even thrive under conditions found beyond their current distributions alters extinction risks, time lags in realizing those risks, and the usefulness of alternative management strategies. To inform these issues, we propose a conceptual framework within which empirical data could be used to generate hypotheses regarding the realized, fundamental, and ‘tolerance’ niche of species. Although these niche components have rarely been characterized over geographic scales, we suggest that this could be done for many plant species by comparing native, naturalized, and horticultural distributions.

Many non-native plants in the US have become problematic invaders of native and managed ecosystems, but a new generation of invasive species may be at our doorstep. Here, we review trends in the horticultural trade and invasion patterns of previously introduced species and show that novel species introductions from emerging horticultural trade partners are likely to rapidly increase invasion risk. At the same time, climate change and water restrictions are increasing demand for new types of species adapted to warm and dry environments. This confluence of forces could expose the US to a range of new invasive species, including many from tropical and semiarid Africa as well as the Middle East. Risk assessment strategies have proven successful elsewhere at identifying and preventing invasions, although some modifications are needed to address emerging threats. Now is the time to implement horticulture import screening measures to prevent this new wave of plant invasions.

This study aims to document shifts in the latitudinal distributions of non-native species relative to their own native distributions and to discuss possible causes and implications of these shifts. We used published and newly compiled data on intercontinentally introduced birds, mammals and plants. We found strong correlations between the latitudinal distributions occupied by species in their native and exotic ranges. However, relatively more non-native species occur at latitudes higher than those in their native ranges, and fewer occur at latitudes lower than those in their native ranges. Only a small fraction of species examined (i.e.\20% of animals and\10% of plants) have expanded their distributions in their exotic range beyond both high- and low-limits of their native latitudes. Birds, mammals and plants tended to shift their exotic ranges in similar ways. In addition, most non-native species (65–85% in different groups) have not reached the distributional extent observed in their native ranges. The possible drivers of latitudinal shifts in the exotic range may include climate change, greater biotic resistance at lower latitudes, historical limitations on ranges in native regions, and the impacts of humans on species distributions. The relatively restricted distribution of most species in their exotic range highlights the great potential of future spread of most introduced species and calls for closely monitoring their directional spread under climate change.

Managed relocation is defined as the movement of species, populations, or genotypes to places outside the areas of their historical distributions to maintain biological diversity or ecosystem functioning with changing climate. It has been claimed that a major extinction event is under way and that climate change is increasing its severity. Projections indicating that climate change may drive substantial losses of biodiversity have compelled some scientists to suggest that traditional management strategies are insufficient. The managed relocation of species is a controversial management response to climate change. The published literature has emphasized biological concerns over difficult ethical, legal, and policy issues. Furthermore, ongoing managed relocation actions lack scientific and societal engagement. Our interdisciplinary team considered ethics, law, policy, ecology, and natural resources management to identify the key issues of managed relocation relevant for developing sound policies that support decisions for resource management. We recommend that government agencies develop and adopt best practices for managed relocation.

Extreme climatic events (ECEs) – such as unusual heat waves, hurricanes, floods, and droughts – can dramatically affect ecological and evolutionary processes, and these events are projected to become more frequent and more intense with ongoing climate change. However, the implications of ECEs for biological invasions remain poorly understood. Using concepts and empirical evidence from invasion ecology, we identify mechanisms by which ECEs may influence the invasion process, from initial introduction through establishment and spread. We summarize how ECEs can enhance invasions by promoting the transport of propagules into new regions, by decreasing the resistance of native communities to establishment, and also sometimes by putting existing non-native species at a competitive disadvantage. Finally, we outline priority research areas
and management approaches for anticipating future risks of unwanted invasions following ECEs. Given predicted increases in both ECE occurrence and rates of species introductions around the globe during the coming decades, there is an urgent need to understand how these two processes interact to affect ecosystem composition and functioning.

Forecasts of species endangerment under climate change usually ignore the processes by which species ranges shift. By analysing the 'climate paths' that range shifts might follow, and two key range-shift processes--dispersal and population persistence--we show that short-term climatic and population characteristics have dramatic effects on range-shift forecasts. By employing this approach with 15 amphibian species in the western USA, we make unexpected predictions. First, inter-decadal variability in climate change can prevent range shifts by causing gaps in climate paths, even in the absence of geographic barriers. Second, the hitherto unappreciated trait of persistence during unfavourable climatic conditions is critical to species range shifts. Third, climatic fluctuations and low persistence could lead to endangerment even if the future potential range size is large. These considerations may render habitat corridors ineffectual for some species, and conservationists may need to consider managed relocation and augmentation of in situ populations.

Managed relocation (MR) has rapidly emerged as a potential intervention strategy in the toolbox of biodiversity management under climate change. Previous authors have suggested that MR(also referred to as assisted colonization, assisted migration, or assisted translocation) could be a last-alternative option after interrogating a linear decision tree. We argue that numerous interacting and value-laden considerations demand a more inclusive strategy for evaluating MR. The pace of modern climate change demands decision making with imperfect information, and tools that elucidate this uncertainty and integrate scientific information and social values are urgently needed. We present a heuristic tool that incorporates both ecological and social criteria in a multidimensional decision-making framework. For visualization
purposes, we collapse these criteria into 4 classes that can be depicted in graphical 2-D space. This framework offers a pragmatic approach for summarizing key dimensions of MR: capturing uncertainty in the evaluation criteria, creating transparency in the
evaluation process, and recognizing the inherent tradeoffs that different stakeholders bring to evaluation of MR and its alternatives.

1. Large-scale conservation planning requires the identification of priority areas in which species have a high likelihood of long-term persistence. This typically requires high spatial resolution data on species and their habitat. Such data are rarely available at a large geographical scale, so distribution modelling is often required to identify the locations of priority areas. However, distribution modelling may be difficult when a species is either not recorded, or not present, at many of the locations that are actually suitable for it. This is an inherent problem for species that exhibit metapopulation dynamics.

2. Rather than basing species distribution models on species locations, we investigated the consequences of predicting the distribution of suitable habitat, and thus inferring species presence/absence. We used habitat surveys to define a vegetation category which is suitable for a threatened species that has spatially dynamic populations (the butterfly Euphydryas aurinia), and used this as the response variable in distribution models. Thus, we developed a practical strategy to obtain high resolution (1 ha) large scale conservation solutions for E. aurinia
in Wales, UK.

3. Habitat-based distribution models had high discriminatory power. They could generalize over a large spatial extent and on average predicted 86% of the current distribution of E. aurinia in Wales. Models based on species locations had lower discriminatory power and were poorer at generalizing throughout Wales.

4. Surfaces depicting the connectivity of each grid cell were calculated for the predicted distribution of E. aurinia habitat. Connectivity surfaces provided a distance-weighted measure of the concentration of habitat in the surrounding landscape, and helped identify areas where the persistence of E. aurinia populations is expected to be highest. These identified successfully known areas of high conservation priority for E. aurinia. These connectivity surfaces allow conservation planning to take into account long-term spatial population dynamics, which would be impossible without being able to predict the species’ distribution over a large spatial extent.

5. Synthesis and applications. Where species location data are unsuitable for building high resolution predictive habitat distribution models, habitat data of sufficient quality can be easier to collect. We show that they can perform as well as or better than species data as a response variable. When coupled with a technique to translate distribution model predictions into landscape priority (such as connectivity calculations), we believe this approach will be a powerful tool for large-scale conservation planning.

A key question facing conservation biologists is whether declines in species' distributions are keeping pace with landscape change, or whether current distributions overestimate probabilities of future persistence. We use metapopulations of the marsh fritillary butterfly Euphydryas aurinia in the United Kingdom as a model system to test for extinction debt in a declining species. We derive parameters for a metapopulation model (incidence function model, IFM) using information from a 625-km2 landscape where habitat patch occupancy, colonization, and extinction rates for E. aurinia depend on patch connectivity, area, and quality. We then show that habitat networks in six extant metapopulations in 16-km2 squares were larger, had longer modeled persistence times (using IFM), and higher metapopulation capacity (λM) than six extinct metapopulations. However, there was a >99% chance that one or more of the six extant metapopulations would go extinct in 100 years in the absence of further habitat loss. For 11 out of 12 networks, minimum areas of habitat needed for 95% persistence of metapopulation simulations after 100 years ranged from 80 to 142 ha (∼5–9% of land area), depending on the spatial location of habitat. The area of habitat exceeded the estimated minimum viable metapopulation size (MVM) in only two of the six extant metapopulations, and even then by only 20%. The remaining four extant networks were expected to suffer extinction in 15–126 years. MVM was consistently estimated as ∼5% of land area based on a sensitivity analysis of IFM parameters and was reduced only marginally (to ∼4%) by modeling the potential impact of long-distance colonization over wider landscapes. The results suggest a widespread extinction debt among extant metapopulations of a declining species, necessitating conservation management or reserve designation even in apparent strongholds. For threatened species, metapopulation modeling is a potential means to identify landscapes near to extinction thresholds, to which conservation measures can be targeted for the best chance of success.

1. Faced with unpredictable environmental change, conservation managers face the dual challenges of protecting species throughout their ranges and protecting areas where populations are most likely to persist in the long term. The former can be achieved by protecting locally rare species, to the potential detriment of protecting species where they are least endangered and most likely to survive in the long term.
. 2. Using British butterflies as a model system, we compared the efficacy of two methods of identifying persistent areas of species’ distributions: a single-species approach and a new multispecies prioritization tool called ZONATION. This tool identifies priority areas using population dynamic principles (prioritizing areas that contain concentrations of populations of each species) and the reserve selection principle of complementarity.
. 3. ZONATION was generally able to identify the best landscapes for target (i.e. conservation priority) species. This ability was improved by assigning higher numerical weights to target species and implementing a clustering procedure to identify coherent biological management units.
. 4. Weighting British species according to their European rather than UK status substantially increased the protection offered to species at risk throughout Europe. The representation of species that are rare or at risk in the UK, but not in Europe, was not greatly reduced when European weights were used, although some species of UK-only concern were no longer assigned protection inside their best landscapes. The analysis highlights potential consequences of implementing parochial vs. wider-world priorities within a region.
. 5. Synthesis and applications. Wherever possible, reserve planning should incorporate an understanding of population processes to identify areas that are likely to support persistent populations. While the multispecies prioritization tool ZONATION compared favourably to the selection of ‘best’ areas for individual species, a user-defined input of species weights was required to produce satisfactory solutions for long-term conservation. Weighting species can allow international conservation priorities to be incorporated into regional action plans but the potential consequences of any putative solution should always be assessed to ensure that no individual species of local concern will be threatened.

Across large parts of the world, wildlife has to coexist with human activity in highly modified and fragmented landscapes. Combining concepts from population viability analysis and spatial reserve design, this study develops efficient quantitative methods for identifying conservation core areas at large, even national or continental scales. The proposed methods emphasize long-term population persistence, are applicable to both fragmented and natural landscape structures, and produce a hierarchical zonation of regional conservation priority. The methods are applied to both observational data for threatened butterflies at the scale of Britain and modelled probability of occurrence surfaces for indicator species in part of Australia. In both cases, priority landscapes important for conservation management are identified. © 2005 the Royal Society.