ENDOTHERMY, THERMAL NICHE EVOLUTION AND THE DISTRIBUTION OF VERTEBRATE DIVERSITY

Understanding the mechanisms by which the abiotic and biotic requirements of species, or ecological niches, evolve over time is a central issue in evolutionary biology. Niche evolution is poorly understood at both the macroecological and macroevolutionary scales because niches can shift over short periods of time but appear to evolve more slowly at longer time scales. Although reconstructing past niches has always been a major concern for paleontologists and evolutionary biologists, only a few recent studies have successfully determined the factors that affect niche evolution. Here, we compare the evolution of climatic niches in four main groups of terrestrial vertebrates using a novel modeling approach and large-scale datasets that contain information on the current distributions, phylogenetic relationships and fossil records for a total of 11,465 species. By reconstructing historical shifts in geographical ranges and climatic niches, we show that niche shifts are up to five times faster on average in endotherms (birds and mammals) than in ectotherms (squamates and amphibians). We further demonstrate that the diversity patterns of the four clades are directly affected by the rate of niche evolution, with less latitudinal shifts in ectotherms. Our results have implications for conservation efforts by suggesting that adaptation to changing climate may take longer for ectotherms than for endotherms.