Coevolution between heat and cold tolerance in endotherms.

This article investigates the evolutionary relationship between heat and cold tolerance in endotherms, focusing on whether these thermal limits evolve independently or correlatively. Using a phylogenetic comparative approach and a database of thermal neutral zone (TNZ) data from 552 bird and mammal species, the study found a significant positive correlation between upper (heat tolerance) and lower (cold tolerance) thermal limits across endotherms. This coevolutionary pattern is phylogenetically constrained in tropical species but not in temperate ones, suggesting that evolutionary history plays a stronger role in shaping thermal tolerance in tropical endotherms. The findings imply that both physiological trade-offs and natural selection may contribute to this pattern, which has implications for understanding species' responses to climate change and their future evolutionary trajectories.