Phylogeny and morphology determine vulnerability to global warming in Pristimantis frogs

Global warming is a great threat to biodiversity with negative impacts spanning the entire biological hierarchy. One of the main species’ traits determining survival at higher temperature is the thermal point at which an animal loses its ability to escape from deadly conditions (critical thermal maximum—CTmax). Variation in CTmax across species is the outcome of environmental and evolutionary factors, but studies do not typically measure the degree to which environment or phylogeny influences the variation in trait values. Here, we aim to elucidate whether local environmental variables or phylogeny influence CTmax in highly climate change-threatened amphibians in the Tropical Andes. We measured CTmax from 204 individuals belonging to seven Pristimantis frog species encountered in primary and secondary forests, and cattle pastures. We recorded their habitat, elevation, and the range of environmental temperatures they experienced over one year. Using phylogenetic analyses, we demonstrate that physiological thermal tolerance is related to phylogeny, positively related to body length, but not affected by environmental factors. We suggest that both phylogeny and morphology determine vulnerability to global warming.