Slowing down: A macroevolutionary approach to the hypometabolic strategies of amphibians

The ability to survive harsh environmental conditions has probably been a key factor in the evolutionary success of organisms that cannot migrate long distances, such as amphibians. We expect that having a hypometabolic strategy (HS) --aestivation or hibernation-- to deal with severe climates, would be a plesiomorphic trait. We 1) inferred the ancestral state of a HS, using two phylogenies for amphibians, 2) tested if species with a HS have larger distributional ranges, and 3) explored how a HS may affect amphibian assemblage resilience using multiple models of climate change. Ancestral state reconstruction for the most recent common ancestor (MRCA) of Class Amphibia showed [~]50% probability of a HS. The probability was higher for the MRCA of each Order (>70%), suggesting a widespread HS in the ancestors of modern amphibians. Phylogenetic regressions showed no relation between the probability of having a HS and the distribution range size. Climate analyses predict that tropical zones will have the greatest change in climate, involving novel harsh seasonality. Since tropical amphibian assemblages have the lowest proportion of species with HS, they may be more vulnerable to climate change. It is probable that HS have been key for the evolutionary success in amphibians, and they will likely impact their future survival in the face of climate change. Despite the potential importance of the HS for amphibians, information was available for a diverse but only a small subset of species; we urge researchers to report data on aestivation or hibernation in amphibians to facilitate future studies.