Climate and habitat availability determine 20th century changes in a butterfly's range margin

Evidence of anthropogenic global climate change is accumulating, but its potential consequences for insect distributions have received little attention. We use a ''climate response surface'' model to investigate distribution changes at the northern margin of the speckled wood butterfly, Pararge aegeria. We relate its current European distribution to a combination of three bioclimatic variables. We document that P. aegeria has expanded its northern margin substantially since 1940, that changes in this species'' distribution over the past 100 years are likely to have been due to climate change, and that P. aegeria will have the potential to shift its range margin substantially northwards under predicted future climate change. At current rates of expansion, this species could potentially colonize all newly available climatically suitable habitat in the UK over the next 50 years or more. However, fragmentation of habitats can affect colonization, and we show that availability of habitat may be constraining range expansion of this species at its northern margin in the UK. These lag effects may be even more pronounced in less-mobile species inhabiting more fragmented landscapes, and highlight how habitat distribution will be crucial in predicting species'' responses to future climate change.     

Modelling and analysing evolution of dispersal in populations at expanding range boundaries

Abstract 1. Species would be expected to shift northwards in response to current climate warming, but many are failing to do so because of fragmentation of breeding habitats. Dispersal is important for colonisation and an individual‐based spatially explicit model was developed to investigate impacts of habitat availability on the evolution of dispersal in expanding populations. Model output was compared with field data from the speckled wood butterfly Pararge aegeria, which currently is expanding its range in Britain. 2. During range expansion, models simulated positive linear relationships between dispersal and distance from the seed location. This pattern was observed regardless of quantity (100% to 10% habitat availability) or distribution (random vs. gradient distribution) of habitat, although higher dispersal evolved at expanding range margins in landscapes with greater quantity of habitat and in gradient landscapes. Increased dispersal was no longer evident in any landscape once populations had reached equilibrium; dispersal values returned to those of seed populations. However, in landscapes with the least quantity of habitat, reduced dispersal (below that of seed populations) was observed at equilibrium. 3. Evolutionary changes in adult flight morphology were examined in six populations of P. aegeria along a transect from the distribution core to an expanding range margin in England (spanning a latitudinal distance of >200 km). Empirical data were in agreement with model output and showed increased dispersal ability (larger and broader thoraxes, smaller abdomens, higher wing aspect ratios) with increasing distance from the distribution core. Increased dispersal ability was evident in populations from areas colonised >30 years previously, although dispersal changes were generally evident only in females. 4. Evolutionary increases in dispersal ability in expanding populations may help species track future climate changes and counteract impacts of habitat fragmentation by promoting colonisation. However, at the highest levels of habitat loss, increased dispersal was less evident during expansion and reduced dispersal was observed at equilibrium indicating that, for many species, continued habitat fragmentation is likely to outweigh any benefits from dispersal.     

Macro‐ and microclimatic interactions can drive variation in species' habitat associations

Many species are more restricted in their habitat associations at the leading edges of their range margins, but some species have broadened their habitat associations in these regions during recent climate change. We examine the effects of multiple, interacting climatic variables on spatial and temporal patterns of species' habitat associations, using the speckled wood butterfly, Pararge aegeria, in Britain, as our model taxon. Our analyses reveal that this species, traditionally regarded as a woodland‐dependent insect, is less restricted to woodland in regions with warmer winters and warmer and wetter summers. In addition, over the past 40 years of climate change, the species has become less restricted to woodland in locations where temperature and summer rainfall have increased most. We show that these patterns arise mechanistically because larval growth rates are slower in open (i.e. nonwoodland) habitats associated with colder microclimates in winter and greater host plant desiccation in summer. We conclude that macro‐ and microclimatic interactions drive variation in species' habitat associations, which for our study species resulted predominantly in a widening of habitat associations under climate change. However, species vary in their climatic and nonclimatic requirements, and so complex spatial and temporal patterns of changes in habitat associations are likely to be observed in future as the climate changes.     

Linking habitat use to range expansion rates in fragmented landscapes: a metapopulation approach

Temperature increases because of climate change are expected to cause expansions at the high latitude margins of species distributions, but, in practice, fragmented landscapes act as barriers to colonization for most species. Understanding how species distributions will shift in response to climate change therefore requires techniques that incorporate the combined effects of climate and landscape‐scale habitat availability on colonization rates. We use a metapopulation model (Incidence Function Model, IFM) to test effects of fine‐scale habitat use on patterns and rates of range expansion by the butterfly Hesperia comma. At its northern range margin in Britain, this species has increased its breadth of microhabitat use because of climate warming, leading to increased colonization rates. We validated the IFM by reconstructing expansions in five habitat networks between 1982 and 2000, before using it to predict metapopulation dynamics over 100 yr, for three scenarios based on observed changes to habitat use. We define the scenarios as “cold‐world” (only hot, south‐facing 150–250° hillsides are deemed warm enough), “warm‐world” in which 100–300° hillsides can be populated, and “hot‐world”, where the background climate is warm enough to enable use of all aspects (as increasingly observed). In the simulations, increased habitat availability in the hot‐world scenario led to faster range expansion rates, and to long‐term differences in distribution size and pattern. Thus, fine‐scale changes in the distribution of suitable microclimates led to landscape‐scale changes in population size and colonization rate, resulting in coarse‐scale changes to the species distribution. Despite use of a wider range of habitats associated with climate change, H. comma is still expected to occupy a small fraction of available habitat in 100 yr. The research shows that metapopulation models represent a potential framework to identify barriers to range expansion, and to predict the effects of environmental change or conservation interventions on species distributions and persistence.     

The effect of habitat on the range expansion of a native and an introduced bird species

Aim Range expansion across a heterogeneous landscape may depend on the habitat selected and used by the expanding species. If habitat selection influences range expansion then localities colonized by a species should contain a greater proportion of favoured habitat (and less non‐habitat) than other nearby localities not colonized. White‐winged doves (Zenaida asiatica) and Eurasian collared doves (Streptopelia decaocto) are two bird species that provide an excellent opportunity to test this hypothesis, because the geographic ranges of both species have been expanding in North America for more than two decades. Location Continental USA. Methods We used distribution data from the North American Breeding Bird Survey to test whether the landscapes occupied by each species contained a greater proportion of favoured habitat (urban land, grassland/pasture, shrub land and cropland) and a lower proportion of non‐habitat (forest land) than landscapes where doves were not found. We tested each species separately in each of three broad expansion areas, namely East, Central and West. We also compared rates of spatial spread between expansion areas and between the two species. Results As predicted, both species tended to occupy landscapes with greater proportions of urban land, shrub land and cropland but with less forest land compared with landscapes without doves, in all three expansion areas. Contrary to prediction, occupied landscapes tended to have slightly less grassland/pasture than unoccupied landscapes. Rates of spread differed between the two species and among expansion areas. Main conclusions Range expansion and the extent to which a species fills or saturates its range are influenced by the habitat ecology of the expanding species. Species colonize localities based on the availability of suitable habitat. However, the role of habitat in a species’ range expansion does depend somewhat on the greater geographical setting. Over large regional and geographical scales, range expansion (rate of spread and saturation) may proceed unevenly, suggesting that range expansion is a very dynamic and context‐specific process.     

Quantifying the activity levels and behavioural responses of butterfly species to habitat boundaries

1. The ability of species' to undergo climate‐driven range shifts across fragmented landscapes depends on their dispersal ability as well as the structure of the landscape. For species' range shifts to occur, individuals must first leave suitable habitat to seek new habitat; this is likely to depend on the rate of movement of individuals within habitat and the likelihood that a boundary is crossed, once it is encountered. For three species of butterfly with contrasting histories of recent range expansion, we examined the propensity of individuals to move within a habitat and their responses to habitat boundaries. 2. We quantified the extent to which Plebejus argus (Linnaeus) (a declining habitat specialist), Aricia agestis (Schiffermuller) (an expanding generalist) and Polymmatus icarus (Rottemburg) (a geographically ubiquitous generalist) crossed habitat boundaries into unsuitable habitat and moved within suitable habitat. The observed movement was then related to individual and environmental conditions. 3. Species differed in their activity levels in accordance within their recent distribution patterns (P. icarus > A. agestis > P. argus). Our results for P. argus suggest that movement may be motivated by nectar‐seeking, and that males generally move more than females. All three species tended to avoid crossing habitat boundaries; however the proportion of individuals crossing habitat boundaries did not differ significantly among species. 4. We conclude that levels of activity within a habitat, which will affect the frequency with which individuals encounter habitat boundaries, rather than behavioural responses to the boundaries, may be important drivers of distribution change.     

Climate change‐linked range expansion of Nathusius’ pipistrelle bat,Pipistrellus nathusii (Keyserling & Blasius, 1839)

Aim To examine the effect of climate change on the occurrence and distribution of Pipistrellus nathusii (Nathusius’ pipistrelle) in the United Kingdom (UK). Location We modelled habitat and climatic associations of P. nathusii in the UK and applied this model to the species’ historical range in continental Europe. Methods A binomial logistic regression model was constructed relating the occurrence of P. nathusii to climate and habitat characteristics using historical species occurrence records (1940–2006) and CORINE land cover data. This model was applied to historical and projected climate data to examine changes in suitable range (1940–2080) of this species. We tested the predictive ability of the model with known records in the UK after 2006 and applied the model to the species’ known range in Europe. Results The distribution of P. nathusii was related positively to the area of water bodies, woodland and small areas of urbanization, and negatively related to the area of peat/heathland. Species records were associated with higher minimum temperatures, low seasonal variation in temperature and intermediate rainfall. We found that suitable areas have existed in the UK since the 1940s and that these have expanded. The model had high predictive power when applied to new records after 2006, with a correct classification rate of 70%, estimated by receiver operating characteristic analysis. Based on climate projections, our model suggests a potential twofold increase in the area suitable for P. nathusii in the UK by 2050. The single most influential climate variable contributing to range increase was the projected increase in minimum temperature. When applied to Europe, the model predictions had best predictive capability of known records in western areas of the species’ range, where P. nathusii is present during the winter. Main conclusions We show that a mobile, migratory species has adapted its range in response to recent climate change on a continental scale. We believe this may be the first study to demonstrate a case of range change linked to contemporary climate change in a mammal species in Europe.     

Dynamic distribution modelling: predicting the present from the past

Confidence in projections of the future distributions of species requires demonstration that recently-observed changes could have been predicted adequately. Here we use a dynamic model framework to demonstrate that recently-observed changes at the expanding northern boundaries of three British butterfly species can be predicted with good accuracy. Previous work established that the distributions of the study species currently lag behind climate change, and so we presumed that climate is not currently a major constraint at the northern range margins of our study species. We predicted 1970–2000 distribution changes using a colonisation model, MIGRATE, superimposed on a high-resolution map of habitat availability. Thirty-year rates and patterns of distribution change could be accurately predicted for each species (κ goodness-of-fit of models >0.64 for all three species, corresponding to >83% of grid cells correctly assigned), using a combination of individual species traits, species-specific habitat associations and distance-dependent dispersal. Sensitivity analyses showed that population productivity was the most important determinant of the rate of distribution expansion (variation in dispersal rate was not studied because the species are thought to be similar in dispersal capacity), and that each species' distribution prior to expansion was critical in determining the spatial pattern of the current distribution. In future, modelling approaches that combine climate suitability and spatially-explicit population models, incorporating demographic variables and habitat availability, are likely to be valuable tools in projecting species' responses to climatic change and hence in anticipating management to facilitate species' dispersal and persistence.     

Evaluating the Mechanisms of Landscape Change on White-Tailed Deer Populations

Understanding how landscape change influences the distribution and densities of species, and the consequences of these changes, is a central question in modern ecology. The distribution of white-tailed deer (Odocoileus virginianus) is expanding across North America, and in some areas, this pattern has led to an increase in predators and consequently higher predation rates on woodland caribou (Rangifer tarandus caribou)—an alternate prey species that is declining across western Canada. Understanding the factors influencing deer distribution has therefore become important for effective conservation of caribou in Canada. Changing climate and anthropogenic landscape alteration are hypothesized to facilitate white-tailed deer expansion. Yet, climate and habitat alteration are spatiotemporally correlated, making these factors difficult to isolate. Our study evaluates the relative effects of snow conditions and human-modified habitat (habitat alteration) across space on white-tailed deer presence and relative density. We modeled deer response to snow depth and anthropogenic habitat alteration across a large latitudinal gradient (49° to 60°) in Alberta, Canada, using motion-sensitive camera data collected in winter and spring from 2015 to 2019. Deer distribution in winter and spring were best explained by models including both snow depth and habitat alteration. Sites with shallower snow had higher deer presence regardless of latitude. Increased habitat alteration increased deer presence in the northern portion of the study area only. Winter deer density was best explained by snow depth only, whereas spring density was best explained by both habitat alteration and the previous winter's snow depth. Our results suggest that limiting future habitat alteration or restoring habitat can alter deer distribution, thereby potentially slowing or reversing expansion, but that climate plays a significant role beyond what managers can influence. © 2020 The Wildlife Society.     

Evolution of flight morphology in a butterfly that has recently expanded its geographic range

Individuals colonizing unoccupied habitats typically possess characters associated with increased dispersal and, in insects, colonization success has been related to flight morphology. The speckled wood butterfly, Pararge aegeria, has undergone recent major expansions in its distribution: in the north of its range, P. aegeria has colonized many areas in north and east England, and in the south, it was first recorded on Madeira in 1976. We examined morphological traits associated with flight and reproduction in the northern subspecies tircis, and in the southern subspecies aegeria, from sites colonized about 20 years ago in northern England and on Madeira, respectively. Investment in flight was measured as relative wing area and thorax mass, and investment in reproduction as relative abdomen mass. All measurements were from individuals reared in a common environment and there were significant family effects in most of the variables measured. Compared with individuals from sites continuously occupied in recent history, colonizing individuals were larger (adult live mass). In the subspecies tircis, colonizing individuals also had relatively larger thoraxes and lower wing aspect ratios indicating that evolutionary changes in flight morphology may be related to colonization. However, sex by site interactions in analyses of thorax mass and abdomen mass suggest different selection pressures on flight morphology between the sexes in relation to colonization. Overall, the subspecies aegeria was smaller (adult live mass) and had a relatively larger thorax and wings, and smaller abdomen than subspecies tircis. Evolutionary changes in flight morphology and dispersal rate may be important determinants of range expansion, and may affect responses to future climate change. Received: 1 March 1999 / Accepted: 30 June 1999     

Butterfly habitats, broad-scale biotope affiliations, and structural exploitation of vegetation at finer scales: the matrix revisited

Abstract. 1. Biotope and resources data are rarely attached to arthropod (butterfly) synoptic monitoring systems, and invariably not linked to behavioural exploitation of vegetation substrates. Yet, these data allow us to examine resource use within different biotopes and to distinguish more clearly between habitat and the matrix. 2. Comparative data on vegetation exploitation for different behaviours (search flight, direct flight, tactile inspections, perching, feeding, interactions, oviposition) were collected using transect sections over a range of biotopes from bare ground to mature woodland for two closely related satyrine butterflies, Maniola jurtina and Pyronia tithonus with overlapping flight times. Occupancy data were obtained on Pararge aegeria as a marker for the woodland end of the biotope spectrum. 3. There were clear distinctions in biotope occupancy between M. jurtina (grassland bias) and P. tithonus (shrub bias); significant differences in exploitation of vegetation substrates (except for nectar feeding) coincided with this bias in transect sections which comprise both grassland and shrubs. The exception (nectar feeding) is explained by the decline in shrub (Rubus fruticosus) nectar and increase in herb nectar during the later emergence of P. tithonus. 4. Direct flight increased in unsuitable biotopes for both species. However, resource‐exploiting behaviour (>70%) predominated even in biotopes that would be regarded as completely unsuitable for supporting the species and where less than 2% of individuals for each species were observed. 5. Simultaneous collection of biotope, resources, and behavioural data is needed for monitoring affinities of butterflies to vegetation structures and using butterflies as indicators of environmental changes. 6. Much of the landscape is shown to comprise valuable resources for butterflies, even when classified for metapopulation studies as empty matrix.     

Biological flora of Central Europe: Ceratocapnos claviculata (L.) Lidén

The eu-oceanic therophytic woodland herb Ceratocapnos claviculata has been expanding north- and eastwards into north temperate and subcontinental regions during the past decades. The rapid range expansion of the species may be an example of a species which is strongly profiting from global change. Against this background, in the present paper we review the taxonomy, morphology, distribution, habitat requirements, life cycle and biology of the species.     

Golden Eagle Aquila chrysaetos density and productivity in relation to land abandonment and forest expansion in the Alps

Land abandonment and afforestation are causing considerable forest expansion in the Alpine chain, with consequent loss of Alpine pastures, the main foraging habitat for Golden Eagles Aquila chrysaetos. A population of 46 pairs of Golden Eagles was systematically surveyed between 1984 and 1989 in the central-eastern Italian Alps. We measured the amount of woodland within the potential hunting range of 36 pairs. Nearest-neighbour distance was correlated positively with the extent of woodland within the potential hunting range. Productivity was not significantly affected by the amount of woodland within the potential for-aging range. At current rates of forest expansion, such data suggest a 5–9% density decline in the next 20 years. However, increasing food supply and decreasing human persecution could be masking current effects of habitat loss.     

Geographical variation in host use of a blood-feeding ectoparasitic fly: implications for population invasiveness

Invasive generalist ectoparasites provide a tool to study factors affecting expansion rates. An increase in the number of host species may facilitate geographic range expansion by increasing the number of suitable habitats and by affecting local extinction and colonization rates. A geographic perspective on parasite host specificity and its implications on range expansion are, however, insufficiently understood. We conducted a field study to explore if divergent host specificity could explain the observed variation in expansion rates between Fennoscandian populations of the deer ked (Lipoptena cervi), which is a blood-feeding ectoparasitic fly of cervids. We found that the rapidly expanding eastern population in Finland appears to specialize on moose, whereas the slowly expanding western population in Norway breeds successfully on both moose and roe deer. The eastern population was also found to utilize the wild forest reindeer as an auxiliary host, but this species is apparently of low value for L. cervi in terms of adult maintenance, reproductive output and offspring quality. Abundant numbers of roe deer and white-tailed deer were observed to be apparently uninfected in Finland, suggesting that host use is not a plastic response to host availability, but rather a consequence of population-level evolutionary changes. Locally compatible hosts were found to be the ones sharing a long history with the deer ked in the area. Cervids that sustained adult deer keds also allowed successful reproduction. Thus, host use is probably determined by the ability of the adult to exploit particular host species. We conclude that a wide host range alone does not account for the high expansion rate or wide geographic distribution of the deer ked, although loose ecological requirements would increase habitat availability.     

Invasion dynamics and potential spread of the invasive alien plant species Ageratina adenophora (Asteraceae) in China

Ageratina adenophora (Sprengel) R. King & H. Robinson (=Eupatorium adenophorum Sprengel) is one of the worst invasive alien species in China. Since A. adenophora was first noticed in Yunnan Province of China in the 1940s, its rapid spread has caused an ecological problem in south‐western China. Understanding its historical invasion pattern and its potential for further spread is needed to plan the management of the species. We reconstructed the historical process of its invasion and analysed its ecological preferences in the invaded region. After a lag phase of 20 years (1940–60), A. adenophora spread rapidly throughout the south and middle subtropical zones in Yunnan, Guizhou, Sichuan, and Guangxi, China, with an average expansion rate of 20 km per year. It spread relatively slowly in north subtropical areas, with an average expansion rate of 6.8 km per year. It has not established in warm temperate areas within the invaded regions. Although range expansion in Yunnan stopped after 1990, the expansion of its range into neighbouring provinces indicates that A. adenophora has not reached the full potential of its distribution and its range is still rapidly expanding within China. We applied ecological niche modelling (GARP — Genetic Algorithm for Rule‐set Prediction) to predict potential invasion areas in mainland China on the basis of occurrence points within colonized areas where A. adenophora has reached equilibrium. The predictions, confirmed by the range of values of four key environmental parameters, generally match the parameters of the geography and ecology in the invaded region. Southern and south‐central China have climatic conditions suggestive of a high potential for invasion by A. adenophora. Climatic conditions in northern and western China appear unsuitable for A. adenophora. Urgent measures should be taken to prevent this species from further spreading into the vast areas of potential habitat in southern and south‐central China.     

Encroachment of open grasslands and Acacia drepanolobium Harms ex B.Y.Sjöstedt habitats by Euclea divinorum Hiern in Ol Pejeta Conservancy,Kenya

Euclea divinorum, a fast establishing, unpalatable, and fire resistant bush is considered an invasive species in some parts of its range. In Ol Pejeta Conservancy (OPC), Kenya, E. divinorum bushes cover ?27% of the total area (?9470 ha.) and has been expanding in coverage and encroaching into A. drepanolobium woodlands, a key woody habitat for the endangered black rhino. Between 2006 and 2010, we assessed the spatial distribution, annual rates of spread and recruitment of E. divinorum in OPC. We used data from satellite imagery and belt transects laid at the transition between E. divinorum habitat and other habitats. Density of E. divinorum seedlings increased by 27% annually over five years, with more seedlings establishing in grassland habitat (56.6%) than in A. drepanolobium woodland (43.4%). Within the infection frontier, the number of seedlings was high at the ecotone and reduced predictably with an increase in distance into the infection zone. Increase in rainfall facilitated recruitment and survival of E. divinorum seedlings and also reduced damage on trees and seedlings by mega‐herbivores, especially elephants. This study confirms the encroachment of E. divinorum bushland into other habitats. This has been accelerated by burning and damage to A. drepanolobium habitat thus opening it up to encroachment by E. divinorum.     

Influence of thermal conditions on habitat use by a rare spring‐emerging butterfly Euphydryas editha taylori

We may expect butterflies as ectotherms to have particularly active life‐history stages that occur in the warmest and lightest times of the year; however, there are temperate species that are active when climatic conditions seem unfavourable and photoperiod short, such as the Taylor's checkerspot (Euphydryas editha taylori). For such species, studies suggest that even subtle changes to microclimate can potentially impact populations. Thus, understanding how in situ variations in microclimate influence the Taylor's checkerspot butterfly could provide much needed insights into more effective management. We conducted a series of surveys that explored (i) adult habitat use, (ii) final instar larval distribution and (iii) adult movement up to and across site boundaries at two sites in Oregon, USA, in 2010 and 2011. We found that in situ habitat use by the Taylor's checkerspot butterfly was strongly influenced by microclimate. Both adult activities and final instar larvae distribution were clustered within the warmest areas of the sites. Moreover, adults did not use up to 59% and larva up to 90% of their sites, despite vegetation structure and composition being uniform. More specifically, butterfly habitat use increased with increasing ground temperatures, and we found that areas with the highest ground temperatures were more exposed to direct sunlight. Similarly, we found that butterflies tended to only move through sunlit site boundaries. We conclude that the Taylor's checkerspot is sensitive to changes in its thermal environment at fine spatial scales. Our results highlight the importance of microclimate as an indicator of habitat quality, and establishing the thermal criteria in which species of concern exists may provide valuable insights into the implications of climate change.     

Landscape structure and phenotypic plasticity in flight morphology in the butterfly Pararge aegeria

In evolutionary time, varying environments may lead to different morphs as a result of genetic adaptation and divergence or phenotypic plasticity. Landscapes that differ in the extent of habitat fragmentation may provide different selection regimes for dispersal, but also for other ecological functions. Several studies on flying insects have shown differences in flight morphology between landscapes, but whether such differences result from plastic responses have rarely been tested. We did a reciprocal transplant experiment with offspring of speckled wood butterfly females (Parargeaegeria) from three types of landscape differing in fragmentation: woodland landscape, landscape with woodland fragments and agricultural landscape with only hedgerows. Young caterpillars were allowed to grow individually on potted host grasses in small enclosures under the three landscape conditions (split‐brood design). Mortality in caterpillars was much higher in agricultural landscape compared to the other landscapes. Additive to the effect of landscape of development, landscape of origin also affected mortality rate in a similar way. Flight morphology of the adults resulting from the experiment differed significantly with landscape. Independent of the landscape of origin, males and females that developed in agricultural landscape were the heaviest and had the greatest wing loadings. Females that developed in agricultural landscape had higher relative thorax mass (i.e. greater flight muscle allocation) in line with adaptive predictions on altered dispersal behaviour with type of landscape. In males, relative thorax mass did not respond significantly relative to landscape of development, but males originating from landscape with woodland fragments allocated more into their thorax compared to males from the other types. We found significant G×E interactions for total dry mass and wing loading. Our results suggest the existence of phenotypic plasticity in butterfly flight morphology associated with landscape structure.     

Modelling the effect of habitat fragmentation on range expansion in a butterfly

There is an increasing need for conservation programmes to make quantitative predictions of biodiversity responses to changed environments. Such predictions will be particularly important to promote species recovery in fragmented landscapes, and to understand and facilitate distribution responses to climate change. Here, we model expansion rates of a test species (a rare butterfly, Hesperia comma) in five landscapes over 18 years (generations), using a metapopulation model (the incidence function model). Expansion rates increased with the area, quality and proximity of habitat patches available for colonization, with predicted expansion rates closely matching observed rates in test landscapes. Habitat fragmentation constrained expansion, but in a predictable way, suggesting that it will prove feasible both to understand variation in expansion rates and to develop conservation programmes to increase rates of range expansion in such species.     

Evidence for evolutionary change associated with the recent range expansion of the British butterfly, Aricia agestis, in response to climate change

Poleward range expansions are widespread responses to recent climate change and are crucial for the future persistence of many species. However, evolutionary change in traits such as colonization history and habitat preference may also be necessary to track environmental change across a fragmented landscape. Understanding the likelihood and speed of such adaptive change is important in determining the rate of species extinction with ongoing climate change. We conducted an amplified fragment length polymorphism (AFLP)‐based genome scan across the recently expanded UK range of the Brown Argus butterfly, Aricia agestis, and used outlier‐based (DFDIST and BayeScan) and association‐based (Isolation‐By‐Adaptation) statistical approaches to identify signatures of evolutionary change associated with range expansion and habitat use. We present evidence for (i) limited effects of range expansion on population genetic structure and (ii) strong signatures of selection at approximately 5% AFLP loci associated with both the poleward range expansion of A. agestis and differences in habitat use across long‐established and recently colonized sites. Patterns of allele frequency variation at these candidate loci suggest that adaptation to new habitats at the range margin has involved selection on genetic variation in habitat use found across the long‐established part of the range. Our results suggest that evolutionary change is likely to affect species’ responses to climate change and that genetic variation in ecological traits across species’ distributions should be maximized to facilitate range shifts across a fragmented landscape, particularly in species that show strong associations with particular habitats.