BERDNIKOVS, Sergejs; University of Cincinnati: Aspects of the evolution of sexual dimorphism in the genus Mustela (Carnivora, Mammalia)

The evolutionary basis of morphological differences between the sexes in mammalian species is still debated. Alternative hypotheses for sexual dimorphism include selective mechanisms or the results of phylogenetic constraint. The family Mustelidae is inconsistent with Rensch’s rule because sexual size dimorphism decreases with body size even though males are larger than females. The genus Mustela, containing sixteen species that have varying amount of sexual dimorphism, provides a good test for hypotheses concerning the evolution of sexual dimorphism and examining Rensch’s rule. Data exist for body size, ecology, life history and natural history for fifteen of these species. Using the data from the literature, and both parametric and resampling techniques, Pearson correlation between body size and sexual dimorphism was near zero before accounting for phylogeny for fifteen species. However, working with a subset of eight Palearctic species, which have excellent phylogenetic and morphologic data, the correlation is higher (r = 0.538). This set however lacks any taxa with no sexual dimorphism. These conflicting results, which both support and contradict Rensch’s rule, document the need for a more detailed phylogenetic study of sexual dimorphism in this group.