Scaling of sexual dimorphism in body size and breeding system in primates

Abstract

RENSCH^1,2 showed, more than 20 years ago, that sexual dimorphism in body size tends to increase with increasing body size in various arthropod and avian taxa. Recently, the same positive relationship has been suggested for mammals in general³, and primates in particular⁴. Based on their findings on primates, Clutton-Brock et al.⁴ discussed several possible functional explanations for this relationship, but considered none of them wholly satisfactory. In particular, they rejected the hypothesis that positive allometry in sexual dimorphism in weight may be the product of an association of size and polygyny; they did not present statistical data to that effect, however. I argue here that, on the contrary, there is a strong relationship between polygyny and positive allometry for sexual dimorphism in body size. The evidence is based on an analysis of the relationship between the scaling of sexual dimorphism in body weight and the breeding system for 53 primate species, which in most cases coincide with those chosen by Clutton-Brock et al.⁴ for their study. The findings are incorporated into a multifactorial system on the evolution of sexual dimorphism in body size.