Abstract

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.

Highlights

  • The climate is changing (IPCC, 2013) and a suite of biological responses have been observed, including changes in species’ phenologies (Roy & Sparks, 2000) and spatial distributions (Chen et al, 2011)

  • We investigate the habitat associations of Pararge aegeria, which reaches its leading-edge range margin in Britain and has expanded its distribution here in recent decades (Fig. 1a)

  • The data confirm that the study species varies in its habitat associations from being predominantly a habitat specialist in places with marginal climates, to being a relative habitat generalist in places with more favourable macroclimates

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Summary

Introduction

The climate is changing (IPCC, 2013) and a suite of biological responses have been observed, including changes in species’ phenologies (Roy & Sparks, 2000) and spatial distributions (Chen et al, 2011). Many species show spatial variation in their habitat associations in relation to geographical variation in climate (Anthes et al, 2008; Ashton et al, 2009) and often become more restricted to a narrower set of habitat types at range margins where climatic conditions are marginal for the species (Thomas et al, 1999; Lennon et al, 2002; Oliver et al, 2009). Variation in species’ habitat associations may arise indirectly, for example, if herbivores become restricted to host plants growing in more humid habitats in situations with low rainfall

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