Sexual Selection and Size Dimorphism in Anuran Amphibia

Abstract

Evidence for the presence of sexual selection in anurans suggests that large males should be favored in many species, and yet in the vast majority of species females are larger than males. This is explained in part by the well-documented fact that large females in many species have higher fecundity than do small females. In addition, I argue that energetic constraints on reproductive males, caused by the costs of advertising, maintaining territories, and lowering food intake, can affect body size in species with prolonged breeding periods. A model is proposed that considers all three factors simultaneously. Predictions of the model are:(1) large females in species that breed explosively, (2) relatively larger males in species that breed for intermediate periods, and (3) females that are again larger relative to males in species that breed for extremely prolonged periods. A preliminary test of this model, based on published studies, shows general agreement with the predictions.