Sexual Size Dimorphism in Multiple Traits: An Integrative Perspective in Several Anuran Species

Abstract

Sexual dimorphism is a fascinating phenomenon that showcases the wide variation of characteristics related to life strategies in organisms. It is driven by two key evolutionary processes: sexual selection and natural selection. Anurans provide an excellent opportunity to study the origin and diversification of sexual dimorphism due to their variation in size and secondary sexual characters, as well as their diverse life histories. Here, we compared the morphology of males and females in six anuran species (Ceratophrys cranwelli, Boana pulchella, Leptodactylus luctator, Odontophrynus americanus, Physalaemus biligonigerus, and Rhinella arenarum) inhabiting the same breeding site. Additionally, we employed an allometric approach to assess changes in magnitude of sexually dimorphic traits relative to body size. No common pattern of sexual size dimorphism emerged, with species exhibiting dissimilar combinations of dimorphic and monomorphic traits. These differences in sexual dimorphism could only be partially attributed to specific behaviors or life histories in certain cases. Discordant patterns of allometry between sexes in most species further contributed to observed diversity. Overall, selective forces shaping morphologies of both sexes appear complex, related not solely to trait function, but also to life history differences between sexes. To fully understand mechanisms driving sexual dimorphism, it is crucial to consider multiple factors such as behavior, reproductive strategies, and environmental conditions. Lack of a common pattern and presence of diverse morphological variations among species underscore the complexity of selection on body size.