Data from: Mutation rate evolution in partially selfing and partially asexual organisms

Different factors may influence the evolution of the mutation rate of a species: costs associated with DNA replication fidelity, indirect selection caused by the mutations produced (that should generally favor lower mutation rates, given that most mutations affecting fitness are deleterious) and genetic drift, that may render selection acting on weak mutators inefficient. In this paper, we use a two-locus model to compute the strength of indirect selection acting on a modifier locus that affects the mutation rate towards a deleterious allele at a second, linked locus, in a population undergoing partial selfing or partial clonality. The results show that uniparental reproduction increases the effect of indirect selection for lower mutation rates. Extrapolating to the case of a whole genome with many deleterious alleles and introducing a direct cost a DNA replication fidelity, the results can be used to compute the evolutionarily stable mutation rate U. In the absence of mutational bias towards higher U, the analytical prediction fits well with individual-based, multilocus simulation results. When such a bias is added into the simulations, however, genetic drift may lead to the maintenance of higher mutation rates, and this effect may be amplified in highly selfing or highly clonal populations due to their reduced effective population size.物种突变率（mutation rate）的演化可受多种因素影响：与DNA复制保真性（DNA replication fidelity）相关的代价、由产生的突变所引发的间接选择（indirect selection）——鉴于大多数影响适合度（fitness）的突变为有害突变，这类间接选择通常会倾向于选择更低的突变率——以及遗传漂变（genetic drift），后者可能使作用于弱突变体的选择效率降低。本文采用双位点模型（two-locus model），计算在部分自交或部分无性繁殖的种群中，作用于修饰位点（modifier locus）的间接选择强度；该修饰位点会影响第二个连锁位点（linked locus）上有害等位基因（deleterious allele）的突变率。研究结果表明，单亲繁殖（uniparental reproduction）会增强针对更低突变率的间接选择效应。将该结论外推至携带多个有害等位基因的全基因组场景，并引入DNA复制保真性的直接代价后，可利用本研究结果计算进化稳定突变率（evolutionarily stable mutation rate）U。在不存在向更高U值的突变偏倚（mutational bias）的情况下，解析预测结果与基于个体的多位点模拟（individual-based multilocus simulation）结果吻合度较高；但若在模拟中引入此类突变偏倚，遗传漂变则可能导致更高突变率的维持，且由于有效种群大小（effective population size）降低，高自交率或高无性繁殖率种群中的这一效应会被进一步放大。