Mutation-selection balance and mixed mating with asexual reproduction

The effects of asexual reproduction on both the number of deleterious mutations per gamete and the mean fitness under mutation-selection balance are investigated. We use two simulation models, considering both finite and infinite populations. The two models incorporate asexual reproduction with varying levels of outcrossing and selfing, degrees of dominance and selection coefficients. The values for mean fitness and number of deleterious mutations per gamete are compared within and among finite and infinite populations to identify the effect of asexual reproduction on levels of load, and how asexual reproduction may interact with genetic drift (population size). Increasing asexual reproduction resulted in an increase in mean fitness and a decrease in the average number of deleterious mutations per gamete for both nearly recessive and additive alleles in both the infinite and finite simulations. Increased mean fitness with increasing asexuality is possibly due to two interacting forces: a greater opportunity for selection to act on heterozygous versus homozygous mutations and the shielding of a proportion of the population from meiotic mutations due to asexual reproduction. The results found here highlight the need to consider asexual reproduction along with mixed mating in models of genetic load and mutation-selection balance.

► Two simulation models developed to investigate effects of asexual reproduction on mutation load.
► Both infinite (no drift) and finite (includes genetic drift) populations are considered.
► Asexual reproduction increased mean fitness and decreased the number of deleterious mutations per gamete.
► Positive effect of asexual reproduction is due to two interacting forces.
► These forces are selection against heterozygotes in asexuals and shielding from meiotic mutations.