Covariance between testes size and substitution rates in primates.

Understanding the causes of substitution rate variation is an important goal in the study of molecular evolution. It has been proposed that sperm competition intensity may affect genome-wide rates of substitution as a by-product of selection on sperm numbers. Here, I test this hypothesis by applying recently developed Bayesian methods to a data set consisting of approximately 35 kb of sequence data from 55 primate species. I find evidence for positive covariance between testes mass and the rate of substitution, independently of the potentially confounding effects of body mass and longevity.