title: Similarities in butterfly emergence dates among populations suggest local adaptation to climate.
abstract: Phenology shifts are the most widely cited examples of the biological impact of climate change, yet there are few assessments of potential effects on the fitness of individual organisms or the persistence of populations. Despite extensive evidence of climate-driven advances in phenological events over recent decades, comparable patterns across species' geographic ranges have seldom been described. Even fewer studies have quantified concurrent spatial gradients and temporal trends between phenology and climate. Here we analyse a large data set (~129 000 phenology measures) over 37 years across the UK to provide the first phylogenetic comparative analysis of the relative roles of plasticity and local adaptation in generating spatial and temporal patterns in butterfly mean flight dates. Although populations of all species exhibit a plastic response to temperature, with adult emergence dates earlier in warmer years by an average of 6.4 days per °C, among-population differences are significantly lower on average, at 4.3 days per °C. Emergence dates of most species are more synchronised over their geographic range than is predicted by their relationship between mean flight date and temperature over time, suggesting local adaptation. Biological traits of species only weakly explained the variation in differences between space-temperature and time-temperature phenological responses, suggesting that multiple mechanisms may operate to maintain local adaptation. As niche models assume constant relationships between occurrence and environmental conditions across a species' entire range, an important implication of the temperature-mediated local adaptation detected here is that populations of insects are much more sensitive to future climate changes than current projections suggest.
authors.affiliation: Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK.
authors.forename: David B
authors.initials: DB
authors.lastname: Roy
authors.affiliation: Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK.
authors.forename: Tom H
authors.initials: TH
authors.lastname: Oliver
authors.affiliation: Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK.
authors.forename: Marc S
authors.initials: MS
authors.lastname: Botham
authors.affiliation: Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK.
authors.forename: Bjorn
authors.initials: B
authors.lastname: Beckmann
authors.affiliation: Butterfly Conservation, Manor Yard, East Lulworth, Wareham, Dorset, BH20 5QP, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Brereton
authors.affiliation: Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK.|Institute for Environment, Sustainability and Regeneration, Staffordshire University, Room s122, Mellor Building, College Road, Stoke on Trent, ST4 2DE, UK.
authors.forename: Roger L H
authors.initials: RL
authors.lastname: Dennis
authors.affiliation: Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Harrower
authors.affiliation: Institute of Evolutionary Biology, The King's Buildings, Edinburgh, EH9 3JT, UK.
authors.forename: Albert B
authors.identifier: http://orcid.org/0000-0002-6553-1553
authors.initials: AB
authors.lastname: Phillimore
authors.affiliation: Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Thomas
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D002080:Butterflies / Q000502:physiology*; D002980:Climate; D057231:Climate Change; D010802:Phylogeny; D011157:Population Dynamics; D012621:Seasons; D013696:Temperature; D006113:United Kingdom
keywords: butterfly monitoring scheme; climate change; life history; local adaptation; phenology; plasticity; temperature; traits