Climate change is increasing temperature variability and is occurring faster than many species can adapt. Thus, thermal breadth, the range of body temperatures over which organisms perform well, and thermal acclimation, the ability to alter optimal performance temperature (Topt) and critical thermal maximum (CTmax) or minimum with changing temperatures (i.e. phenotypic plasticity), reflect the capacity of organisms to respond to temperature variability and are thus crucial species’ traits for coping with climate change. However, there is no theoretical framework for predicting thermal breadths and acclimation across taxa, latitudes, body sizes, traits, and habitats. Here, we address this knowledge gap by using mathematical modeling and empirical analyses across taxa, latitudes, body sizes (13 orders of magnitude), traits, and habitats of 2,445 thermal response curves of ectotherms and 1,040 CTmaxs of amphibians.
Results/Conclusions
We show that time to acclimate for both Topt and CTmax scales positively with body size and this drives the wider thermal breadths of small organisms. Our simple mathematical model of thermal breadths and acclimation recreates salient patterns in thermal breadth and acclimation in our two datasets, and reveals that acclimation abilities, and thus capacities to cope with climate change, have been regularly underestimated for both small and large organisms. Additionally, our analysis reveals that (all else being equal) large-bodied tropical species are at greatest risk from climate change because of their limited acclimation abilities, slow acclimation rates, and narrow thermal breadths. To further validate our model, we show that large tropical amphibians are already more at risk from climate change (based on their current IUCN conservation status) than any other amphibian group tested. In conclusion, we provide biologists and wildlife managers with a validated, mechanistic, and global quantitative framework to predict the thermal breadths and acclimation abilities of species and thus their risk from climate change.