Fixation probability in a diploid sexually reproducing population

Classical population genetics models with haploid individuals and cloning reproduction, such as the Moran process, have limited power in predicting the evolutionary fate of mutants in diploid, sexually reproducing populations. In this work, we built a new stochastic population genetics model to fill this outstanding knowledge gap. We showed that sexual reproduction tends to suppress the fixation probability of beneficial mutants than clonal reproduction, except under overdominance. This effect is particularly large in small populations with biased sex ratios. We also found that small populations are prone to the invasion of mildly detrimental alleles when the heterozygotes have a fitness advantage. Our study highlights the pressing need to extend the research of stochastic population dynamics to consider the biology of sexual reproduction, such as allelic interactions and biased sex ratio. Our model extends the frontier of population genetics research into diploid, sexually reproducing populations and sets the foundation to explore the great variety of biological factors and processes, such as sexual selection and sexual conflict, on stochastic evolutionary dynamics. Future research in this direction will help make better predictions of the evolutionary fate of mutants in relevant contexts, including the conservation of endangered species and evolutionary rescue.