Local adaptation in thermal tolerance for a tropical butterfly across ecotone and rainforest habitats.

Michel A K Dongmo,K K M Fiaboe,Timothy C Bonebrake,Rachid Hanna,Abraham Fomena,Thomas B Smith

doi:10.1242/bio.058619

Abstract

ABSTRACTThermal adaptation to habitat variability can determine species vulnerability to environmental change. For example, physiological tolerance to naturally low thermal variation in tropical forests species may alter their vulnerability to climate change impacts, compared with open habitat species. However, the extent to which habitat-specific differences in tolerance derive from within-generation versus across-generation ecological or evolutionary processes are not well characterized. Here we studied thermal tolerance limits of a Central African butterfly (Bicyclus dorothea) across two habitats in Cameroon: a thermally stable tropical forest and the more variable ecotone between rainforest and savanna. Second generation individuals originating from the ecotone, reared under conditions common to both populations, exhibited higher upper thermal limits (CTmax) than individuals originating from forest (∼3°C greater). Lower thermal limits (CTmin) were also slightly lower for the ecotone populations (∼1°C). Our results are suggestive of local adaptation driving habitat-specific differences in thermal tolerance (especially CTmax) that hold across generations. Such habitat-specific thermal limits may be widespread for tropical ectotherms and could affect species vulnerability to environmental change. However, microclimate and within-generation developmental processes (e.g. plasticity) will mediate these differences, and determining the fitness consequences of thermal variation for ecotone and rainforest species will require continued study of both within-generation and across-generation eco-evolutionary processes.This article has an associated First Person interview with the first author of the paper.

Highlights

Study we investigated the role of habitat in structuring thermal limits, critical thermal maximum (CTmax) and minimum (CTmin), for Bicyclus dorothea (Cramer, 1779), a nymphalid butterfly found in both forest and ecotone habitats in many tropical African countries (Dongmo et al, 2017)
We hypothesized that B. dorothea populations from the ecotone would have wider thermal tolerance breadths than forest populations that would be preserved after lab-rearing under common conditions
We collected critical thermal minimum (CTmin) and CTmax data for a total of 399 s generation butterflies originating across all sites

Summary

INTRODUCTION

It is presently widely accepted that ongoing climate warming has clear and widespread consequences for biodiversity including local extinction, population declines, shifts in community structure and. Recent studies in tropical ecosystems have found that forest species of ectotherms tend to have lower tolerance to warming because they are restricted to more stable thermal regimes and might be especially vulnerable to climate change compared with more open habitat species (Huey et al, 2009; Frishkoff et al, 2015; Bonebrake et al, 2016; Nowakowski et al, 2017). We hypothesized that B. dorothea populations from the ecotone would have wider thermal tolerance breadths than forest populations (reflecting the greater thermal variation in those environments) that would be preserved after lab-rearing under common conditions

RESULTS

DISCUSSION

MATERIAL AND METHODS