Johnson T
Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, Scotland.
Genetics. 1999 Apr;151(4):1621-31. doi: 10.1093/genetics/151.4.1621.
Natural selection acts in three ways on heritable variation for mutation rates. A modifier allele that increases the mutation rate is (i) disfavored due to association with deleterious mutations, but is also favored due to (ii) association with beneficial mutations and (iii) the reduced costs of lower fidelity replication. When a unique beneficial mutation arises and sweeps to fixation, genetic hitchhiking may cause a substantial change in the frequency of a modifier of mutation rate. In previous studies of the evolution of mutation rates in sexual populations, this effect has been underestimated. This article models the long-term effect of a series of such hitchhiking events and determines the resulting strength of indirect selection on the modifier. This is compared to the indirect selection due to deleterious mutations, when both types of mutations are randomly scattered over a given genetic map. Relative to an asexual population, increased levels of recombination reduce the effects of beneficial mutations more rapidly than those of deleterious mutations. However, the role of beneficial mutations in determining the evolutionarily stable mutation rate may still be significant if the function describing the cost of high-fidelity replication has a shallow gradient.
自然选择通过三种方式作用于突变率的可遗传变异。增加突变率的修饰等位基因：（i）由于与有害突变相关联而不受青睐，但也因（ii）与有益突变相关联以及（iii）较低保真度复制成本的降低而受到青睐。当一个独特的有益突变出现并扩散至固定时，基因搭便车可能会导致突变率修饰因子的频率发生实质性变化。在先前关于有性种群中突变率进化的研究中，这种效应被低估了。本文对一系列此类搭便车事件的长期效应进行了建模，并确定了对修饰因子产生的间接选择强度。当这两种类型的突变随机分布在给定的遗传图谱上时，将此结果与有害突变导致的间接选择进行比较。相对于无性种群，重组水平的提高比有害突变更快地降低了有益突变的影响。然而，如果描述高保真复制成本的函数梯度较浅，有益突变在决定进化上稳定的突变率方面的作用可能仍然很显著。
