Thermal tolerance and altitudinal extent across latitude: Testing the effects of seasonality on the distribution of species

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 replace each other more rapidly in the tropics because in many taxa, tropical species have smaller altitudinal extents compared to their temperate counterparts. Theoretical and empirical data suggest that annual temperature variation (seasonality) may be important in setting the altitudinal range, and therefore turnover, of species along mountain ranges, but strong tests are lacking. Here I compare and contrast the altitudinal extent and thermal tolerance of tropical and temperate beetles in relation to the seasonality they experience. Results show that while beetles in tropical areas may show reduced thermal tolerance, they do not necessarily have a smaller altitudinal range. Ecological factors, particularly soil type, may play a greater role in limiting distribution than seasonality alone.