Monte Carloin silicoexperiments uncover a novel mechanism underlying the evolution of mutation rates in sexually reproducing populations

AbstractNatural selection is believed to universally work to lower mutation rates (MR) due to the negative impact of mutations on individual fitness. Mutator alleles have been found to be co-selected by genetic linkage with adaptive alleles in asexual organisms. However, sexual reproduction substantially reduces genetic linkage, allowing selection to efficiently eradicate mutator alleles. The current understanding, therefore, largely postulates that in sexually reproducing populations selection always works to lower MR, limited by the effective population size that determines the overall selection efficiency. In the present paper, we applyin silicoexperimentation based on the Monte Carlo approach of a sexually reproducing population and demonstrate that selection acting on MR does not universally favor lower MR but depends on the mode of selection acting on adaptive phenotypic traits. We demonstrate a unique previously unreported co-selective process that can drive the evolution of higher MR in sexually reproducing populations. Our results show that MR evolution is also significantly influenced by multigenic inheritance of both MR and adaptive traits. Our study corroborates that MR evolution is significantly impacted by genetic drift; however, its primary source appears to be the amount of genetic variation present in the population under selection, with a lesser role for population size. Based on our study, we propose an expanded population genetics theory of the evolution of mutation rates in sexually reproducing populations. Our results have potential implications for understanding processes underlying rapid adaptive change in speciation and related macroevolutionary patterns.