Sexual selection on males predicts reduced mitochondrial genetic diversity across mammals

Sexual selection on males is expected to reduce genetic diversity via paternal inheritance because increased variance in male reproductive success lowers the male effec tive population siz e. It is plausible that sexual selection on males also affec t s ge- netic diversity via maternal inheritance, e.g., due to demographic processes. However, associations between sexual selection and maternally inherited genetic diversity were never tested for. Here, taking advantage of the fact that mitochondria are ma- ternally inherited, we compare the diversity of two widely studied mitochondrial genes across 262 species of non-flying terres- trial mammals, for which male-biased sexual dimorphism is a good indicator of the intensity of sexual selection on males. We found that species with stronger male-biased dimorphism have lower mitochondrial diversity, after controlling for confound- ing effec t s. A plausible explanation f or this r esult is that sexual selec tion on males c an r educe f emale effec tive population size, giving rise to the change of allelic diversity in these mitochondrial genes. Our result thus suggests broader associations of sexual selection with demography and population genetic structure than previously recognized.