Interference among deleterious mutations favours sex and recombination in finite populations
Interference among deleterious mutations favours sex and recombination in finite populations
复制标题
DOI：
10.1038/nature05049
复制
发表时间：
2006-09-07
期刊：
影响因子：
64.8
通讯作者：
Otto, Sarah P.
中科院分区：
文献类型：
--
作者：
Keightley, Peter D.;Otto, Sarah P.
性和重组是普遍存在的，但解释这些现象一直是进化生物学中最困难的问题之一。当群体中的不同个体携带不同的有利等位基因时，重组是有利的（1,2）。通过将优势等位基因聚集到同一染色体上，重组加速了适应过程（1,3-5），并通过穆勒棘轮（Muller’s ratchet）反对有害突变的固定（4,5）。然而，适应性替代只有在适应性突变率高的情况下才有利于性别和重组（1,6），而穆勒棘轮只在小型或无性种群中起作用(7)。在这里，通过追踪改变性别和重组频率的修饰等位基因的命运，我们表明，针对有害突变等位基因的背景选择为性别和重组提供了随机优势，这种优势随着群体规模的增加而增加。这种优势的产生是因为，在低水平的重组下，其他位点的选择严重减少了有效的群体规模和焦点位点的遗传变异（Hill-Robertson效应），使群体对选择的反应能力降低，并消除了有害的突变。性和重组通过结合中间适应度的染色体来产生相对没有（或携带）有害突变的染色体，从而揭示了适应度中隐藏的遗传变异。有限种群中遗传变异的增加改善了对选择的反应，并对性别和重组产生了实质性的优势，这种优势对有害等位基因之间的上位相互作用形式相当不敏感。我们的研究结果支持的机制为重组的进化优势提供了一个强有力的、广泛适用的解释，并可以解释昂贵性行为的传播。
Sex and recombination are widespread, but explaining these phenomena has been one of the most difficult problems in evolutionary biology. Recombination is advantageous when different individuals in a population carry different advantageous alleles(1,2). By bringing together advantageous alleles onto the same chromosome, recombination speeds up the process of adaptation(1,3-5) and opposes the fixation of harmful mutations by means of Muller's ratchet(4,5). Nevertheless, adaptive substitutions favour sex and recombination only if the rate of adaptive mutation is high(1,6), and Muller's ratchet operates only in small or asexual populations(7). Here, by tracking the fate of modifier alleles that alter the frequency of sex and recombination, we show that background selection against deleterious mutant alleles provides a stochastic advantage to sex and recombination that increases with population size. The advantage arises because, with low levels of recombination, selection at other loci severely reduces the effective population size and genetic variance in fitness at a focal locus(8) (the Hill-Robertson effect), making a population less able to respond to selection and to rid itself of deleterious mutations. Sex and recombination reveal the hidden genetic variance in fitness by combining chromosomes of intermediate fitness to create chromosomes that are relatively free of (or are loaded with) deleterious mutations. This increase in genetic variance within finite populations improves the response to selection and generates a substantial advantage to sex and recombination that is fairly insensitive to the form of epistatic interactions between deleterious alleles. The mechanism supported by our results offers a robust and broadly applicable explanation for the evolutionary advantage of recombination and can explain the spread of costly sex.