One of the most well-known patterns in biology is the replacement, or turnover, of similar species as one moves up or down in elevation. The rate of replacement along altitudinal gradients is not uniform across the globe. Specifically, species are thought to replace each other more rapidly in the tropics. Theoretical and empirical data suggest that annual temperature variation (seasonality) are important in setting altitudinal range, and therefore turnover, of species along mountain ranges, but strong tests are lacking. In addition, basic principles in physiological ecology suggest that seasonality may differentially impact the distribution of ecotherms when compared to endotherms. Here we analyze the altitudinal range of ectotherms and endotherms across broad latitudinal gradients in relation to the seasonality they experience.
Results show that while the altitudinal range of ectotherms is highly correlated with seasonality, the range of endotherms shows no relationship to the variation in temperature they experience. Metabolic heating and evaporative cooling in endotherms may act to buffer the impact of temperature variation, making other ecological factors more important in setting the range of endotherms than seasonality alone.