Effect of mutation on genetic differentiation among nonequilibrium populations
Effect of mutation on genetic differentiation among nonequilibrium populations
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DOI：
10.1111/j.1558-5646.2008.00453.x
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发表时间：
2008-09-01
期刊：
影响因子：
3.3
通讯作者：
Leimar, Olof
中科院分区：
文献类型：
--
作者：
Ryman, Nils;Leimar, Olof
G（ST）和类似的遗传分化测量方法的有效性一直受到质疑，因为它们依赖于群体内杂合度的数量，这在比较不同突变率位点的分化程度时产生了问题。尽管突变对G（ST）的影响预计在分化的早期阶段很小，但尚不清楚在与共同祖先群体分离后多久，G（ST）在很大程度上不受突变及其对杂合性的影响。我们通过分析无限等位基因突变模型下的基因同一性递推方程来解决这个问题，并推导出在突变-迁移-漂移平衡条件下以及在过渡阶段之前突变对G（ST）的影响可以忽略的条件。一个重要的结果是，在过渡阶段，G（ST）不仅受到突变的影响，而且受到亚群体分化的基础群体的杂合性的影响。突变对G（ST）的影响在分化过程的最开始，即初始杂合度较低时就很显著，而在分化早期，即初始杂合度较高时，突变对G（ST）的影响较弱。因此，严重瓶颈后的分化强烈依赖于突变。Hedrick（2005）提出的标准化的分化度量G'（ST）可能有助于比较稳态条件下不同突变率的位点的分化量，前提是迁移非常低。然而，在许多其他情况下，G'（ST）的使用可能会产生误导，因此应谨慎使用。
The usefulness of G(ST) and similar measures of genetic differentiation has been questioned repeatedly because of their dependence on the amount of heterozygosity within populations, creating problems when comparing degrees of divergence at loci with different mutation rates. Although the effect of mutation on G(ST) is expected to be small in the early phases of divergence, it is unclear for how long after separation from a common ancestral population that G(ST) is largely unaffected by mutation and by the resulting effect on heterozygosity. We address this question through analysis of the recursion equations for gene identity under the infinite allele model of mutation, and derive conditions describing when the effect of mutation on G(ST) can be ignored under mutation-migration-drift equilibrium conditions and during the preceding transition phase. An important result is that during the transition phase G(ST) is not only affected by mutation, but also by the heterozygosity in the base population from which the subpopulations diverged. The effect of mutation on G(ST) is significant from the very start of the divergence process when initial heterozygosity is low, whereas G(ST) is only weakly affected by mutation in the early phases of differentiation when initial heterozygosity is high. Thus, differentiation following a severe bottleneck is strongly dependent on mutation. The standardized measure of differentiation, G'(ST), suggested by Hedrick (2005), may be helpful when comparing amounts of divergence at loci with different mutation rates under steady-state conditions, provided that migration is very low. In many other situations the use of G'(ST) might be misleading, however, and its application should be exercised with caution.