Dr Wenda Cheng1, Dr Shuang Xing1, Dr Akihiro Nakamura2, Dr Timothy Bonebrake1
1The University of Hong Kong, Hong Kong S.A.R., China, 2Xishuangbanna Tropical Botanical Garden, CAS, Menglun, China
Species are adapted to the environments where they are distributed and tropical species inhabiting stable thermal environments are therefore likely to have low cold tolerance, i.e. “mountain passes are higher in the tropics”. Such intolerance of cold is often conserved among species of tropical origin despite distributions that extend into cooler areas, such as subtropical boundaries. In this case, whether other adaptive mechanisms such as behavior and morphology can compensate for lower physiological tolerance to cold is unknown and may provide important insights into climate change impacts. Here, we examined behaviors and body temperatures of butterflies across elevational gradients at multiple sites in China. We tested whether coexisting tropical and widespread butterfly species differ in their thermoregulation ability to respond to cold air temperatures. Based on biophysical models, we used the amount of heat gain from basking as an indicator and incorporated body temperatures, behaviors, and thermoregulatory morphological traits of butterflies sampled in the field. We found that tropical species are more constrained in their activity at low air temperatures. Relative to widespread/temperate species, tropical species also have larger thorax sizes and are more likely to bask at cooler air temperatures. This study highlights the importance of behavior and morphological adaptations in thermoregulation for tropical butterflies in temperate and subtropical environments. These mechanisms allow tropical species to persist in cooler environments but may limit their expansion into higher latitudes and also likely suggests that higher seasonal variability under climate change may render these species particularly vulnerable to cold weather extremes.
Wenda is a postdoc fellow at the University of Hong Kong, he is working on the distributional and behavioral responses of tropical organisms (mainly insects) at species and species assemblage levels.