Sexual dimorphism in Rhinella major (Anura: Bufonidae) from eastern Brazilian Amazonia

Intersexual morphological differences within a species may occur in body size or shape. It reflects the effects of distinctive selective pressures acting differently upon males and females. Sexual selection and differences in life-history strategies between sexes can generate sexual dimorphism in anurans. Considering the relevance of morphological variation studies to provide in-depth knowledge about species and populations, we investigated sexual dimorphism in the toad Rhinella major. Based on 15 measurements of external morphology related to body size and shape, cluster analyses (PCA and Random Forest) and multivariate analysis of variance showed that females were larger than males in SVL. Most of the variation was tied to body size (F-(1,F-41) = 19.07, p < 0.001). Non-significant differences in shape were found. Our analysis points out the necessity of further investigations on the life -history aspects of R. major to understand the role of sexual (e.g., female fecundity) and natural selection (e.g., niche segregation) in explaining the intrasexual divergence in external morphology of this species.