The evolution of sex differences in mandrills (mandrillus sphinx): micro- and macroevolution

Primates show diverse patterns of adaptive color and body size dimorphism produced by inter- and intrasexual selection. However, the specific microevolutionary processes that produce variation in secondary sexual characteristics remain largely unexplored in primates. Furthermore, sexual conflict theory predicts that female and male secondary sexual traits can coevolve in an antagonistic manner and promote speciation. This dissertation explores the microevolution of secondary sexual characteristics in mandrills (Mandrillus sphinx) and the macroevolution of these characters in anthropoid primates. I address the microevolution of mandrill facial coloration and body mass by estimating the heritability, phenotypic selection, and genetic evolution of these traits in a population of semi free-ranging mandrills at the Centre International de Recherches Médicales de Franceville, Gabon (CIRMF). I address the coevolution of female and male secondary sexual characteristics by extending quantitative genetic analyses to phylogenetic comparative methods. I estimate the phylogenetic coevolution of female and male secondary sexual characteristics and the relationship of trait correlations with diversification rates. Results show that (1) facial redness and body mass are heritable in the CIRMF mandrill population, (2) there is good evidence for male intrasexual selection and total selection in both sexes shaping facial redness and body mass at the phenotypic level, but limited evidence for genetic evolution in this population, and (3) there is evidence that sexual conflict promotes female and male secondary sexual character coevolution and species diversification in anthropoid primates. Overall, this dissertation provides evidence for microevolution in coloration and body size in mandrills, and shows how the evolutionary processes operating in mandrill trait evolution may manifest at the macroevolutionary level.