A population under neutral drift is expected to accumulate genetic substitutions at a fixed “molecular clock” rate over time. If the population is well-mixed, a classic result equates the rate of substitution per generation to the probability of mutation per birth. However, this substitution rate can be altered if individual birth and death rates vary by class or by spatial location.
Here we investigate how mating patterns affect the rate of neutral genetic substitution in a diploid, sexually reproducing population. We employ a general mathematical modeling framework that allows for arbitrary mating pattern and spatial structure.
We demonstrate that if survival rates and mating opportunities vary systematically across individuals, the rate of neutral substitution can be either accelerated or slowed. In particular, this can occur in populations with uneven sex ratio at birth, or with reproductive skew.
Our results suggest that estimates of the rate of neutral substitution, in species with uneven sex ratio and/or reproductive skew, may need to take asymmetries in mating opportunity and survival into account.