How hibernation in frogs drives brain and reproductive evolution in opposite directions

Abstract

Environmental seasonality can promote the evolution of larger brains through cognitive and behavioral flexibility but also hamper it when temporary food shortage is buffered by stored energy. Multiple hypotheses linking brain evolution to resource acquisition and allocation have been proposed, albeit separately for different groups of birds or mammals rather than being directly compared within any single group. Here, using direct tissue measurements and experimentally validated brumation (‘hibernation’) parameters, we integrated these hypotheses across frogs in the context of varying brumation duration and its environmental correlates. We show that protracted brumation reduces brain size and instead promotes reproductive investments, likely in response to brumation-dependent changes in the socio-ecological context that ultimately affect the operation of sexual selection and evolution of mating systems. Our results reveal novel insight into the complex processes of brain and reproductive evolution in organisms whose ‘cold-blooded’ metabolism is particularly susceptible to environmental seasonality.