Linear reaction norms of thermal limits in Drosophila: predictable plasticity in cold but not in heat tolerance

1. Thermal limits of ectotherms have been studied extensively and are believed to be evolutionary constrained, leaving ectotherms at risk under future climate change. Phenotypic plasticity may extend the thermal limits, but we lack detailed characterizations of thermal limit reaction norms as well as an understanding of the interspecific variation of these reaction norms. 2. Here we investigated the interspecific variation in phenotypic plasticity of thermal limits in 13 Drosophila species. We obtained high-resolution reaction norms for upper and lower thermal limits across the permissive developmental thermal range (12.5 – 30°C). The estimated phenotypes were then associated (while accounting for phylogeny) with climatic parameters from the species’ distributional range. 3. All species showed linear reaction norms for cold tolerance (CTmin) and heat tolerance (CTmax) across developmental acclimation temperatures. We observed strong beneficial cold acclimation to lower temperature...