MUTATION ACCUMULATION IN FINITE POPULATIONS
MUTATION ACCUMULATION IN FINITE POPULATIONS
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DOI：
10.1093/oxfordjournals.jhered.a111351
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发表时间：
1993-09-01
影响因子：
3.1
通讯作者：
CHARLESWORTH, B
中科院分区：
文献类型：
--
作者：
CHARLESWORTH, D;MORGAN, MT;CHARLESWORTH, B
两个不同的过程导致了有限群体中的突变积累：突变等位基因的固定和穆勒棘轮。在具有紧密连锁的非常小的随机交配种群中，突变等位基因的固定率很高。在重组非常有限的情况下，随机交配种群中每个基因组的低频突变等位基因的数量也会随着时间的推移而增加，而不受固定的影响(穆勒棘轮)。种群规模的增加对棘轮的影响小于固定过程，种群适应度的下降在大于100的种群中由棘轮主导，特别是在突变率较高的种群中。除非重组受到严格限制，否则固定和棘轮都不会产生严重影响。选择参数的差异(选择强度、显性系数)的影响可以用选择对单个座位的相反效应和座位间的关联来解释。更强的选择会减缓突变的积累，尽管平均适应度下降的速度有时会更快。增加突变等位基因的显性系数往往会起到类似的作用。高度近亲交配会减慢棘轮的速度，因为纯合性最低的类别有更高的初始频率，因为近交系群体中突变等位基因纯合表达的增加具有类似于更强选择的效果。在高度近交的种群中，轻微有害突变的固定会加速，但由于突变积累而导致的适合度下降只在非常小的种群中才会迅速，而且总是比无性种群慢得多。讨论了育种系统和重组率对轻微有害等位基因固定分子进化速度的影响。
Two different processes contribute to mutation accumulation in finite populations: fixation of mutant alleles and Muller's ratchet. In very small random-mating populations, and with tight linkage, fixation of mutant alleles occurs at a high rate. With very restricted recombination, the number of low-frequency mutant alleles per genome in random-mating populations also increases over time independently of fixation (Muller's ratchet). Increased population size affects the ratchet less than the fixation process, and the decline in population fitness is dominated by the ratchet in populations of size greater than about 100, especially with high mutation rates. Neither fixation nor the ratchet has serious effects unless recombination is severely restricted. The effects of differences in the selection parameters (strength of selection, dominance coefficient) can be interpreted in terms of opposing effects of selection on individual loci and associations between loci. Stronger selection slows the accumulation of mutations, although a faster decline in mean fitness sometimes results. Increasing the dominance coefficients of the mutant alleles tends to act similarly. High inbreeding slows the ratchet, because with homozygosity there is a higher initial frequency of the least loaded class, as the increased homozygous expression of mutant alleles in inbred populations has effects similar to stronger selection. Fixation of mildly deleterious mutations is accelerated in highly inbred populations, but fitness decline due to mutation accumulation was rapid only in very small populations and was always much slower than for asexual populations. The effects of breeding system and rate of recombination on the rate of molecular evolution by the fixation of slightly deleterious alleles are discussed.