How well populations can cope with global warming will often depend on the evolutionary potential and plasticity of their temperature‐sensitive, fitness‐relevant traits. In Bechstein's bats ( Myotis bechsteinii ), body size has increased over the last decades in response to warmer summers. If this trend continues it may threaten populations as larger females exhibit higher mortality. To assess the evolutionary potential of bod...

Animals often respond to climate change with changes in morphology, e.g., shrinking body size with increasing temperatures, as expected by Bergmann’s rule. Because small body size can have fitness costs for individuals, this trend could threaten populations. Recent studies, however, show that morphological responses to climate change and the resulting fitness consequences cannot be generalized even among related species. In th...