title: Ecological and evolutionary processes at expanding range margins.
abstract: Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded rapidly in association with recent climate warming. We examined four insect species that have expanded their geographical ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety of habitat types that they can colonize, and that two bush cricket species show increased fractions of longer-winged (dispersive) individuals in recently founded populations. Both ecological and evolutionary processes are probably responsible for these changes. Increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started. The emergence of dispersive phenotypes will increase the speed at which species invade new environments, and probably underlies the responses of many species to both past and future climate change.
authors.affiliation: Centre for Biodiversity and Conservation, School of Biology, University of Leeds, Leeds LS2 9JT, UK. c.d.thomas@leeds.ac.uk
authors.forename: C D
authors.initials: CD
authors.lastname: Thomas
authors.forename: E J
authors.initials: EJ
authors.lastname: Bodsworth
authors.forename: R J
authors.initials: RJ
authors.lastname: Wilson
authors.forename: A D
authors.initials: AD
authors.lastname: Simmons
authors.forename: Z G
authors.initials: ZG
authors.lastname: Davies
authors.forename: M
authors.initials: M
authors.lastname: Musche
authors.forename: L
authors.initials: L
authors.lastname: Conradt
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002080:Butterflies / Q000502:physiology*; D002980:Climate; D004463:Ecology; D004739:England; D004777:Environment; D006135:Gryllidae / Q000502:physiology*; D011157:Population Dynamics