The effects of local selection, balanced polymorphism and background selection on equilibrium patterns of genetic diversity in subdivided populations
The effects of local selection, balanced polymorphism and background selection on equilibrium patterns of genetic diversity in subdivided populations
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DOI：
10.1017/s0016672397002954
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发表时间：
1997-10-01
影响因子：
1.5
通讯作者：
Charlesworth, D
中科院分区：
文献类型：
--
作者：
Charlesworth, B;Nordborg, M;Charlesworth, D
采用多位点随机模拟的方法研究了被细分为两个巢的群体的中性遗传多样性水平。该模型包括整个基因组中位点的有害突变，导致“背景选择”，以及通过频率依赖选择或局部选择差异维持多态性的单个位点。这些平衡的多态性诱导连接的中性位点的长聚结时间，因此这些位点的序列多样性在统计平衡下得到增强。我们研究了平衡中性多样性水平如何受到种群细分程度、背景选择存在与否和种群近交水平的影响。并将模拟结果与近似解析公式进行了比较。我们讨论了如何区分平衡选择与局部选择，通过确定是否在多态位点的区域内或之间看到多样性的高峰。这种多样性峰的宽度取决于物种的总种群大小，而不是局部种群大小。研究表明，随着种群的细分，局部选择增强了deme间的多样性，即使在远离多态性位点的中性位点，也能产生比没有选择时更高的F-ST值；在靠近选定位点的位置可以产生非常高的值。背景选择也增加了F-ST，主要是因为种群内多样性的减少，这意味着背景选择的影响可能与本地选择的影响不同。这两种效应在自交种群中都强于异交种群。中性位点之间的连锁不平衡是由平衡和局部选择共同产生的，特别是在自交群体中，由于中性位点与选择性维持的等位基因之间的连锁不平衡。我们讨论了这些理论结果如何与一个物种的本地种群内部和之间的遗传多样性数据相关联。
Levels of neutral genetic diversity in populations subdivided into two demes were studied by multilocus stochastic simulations. The model includes deleterious mutations at loci throughout the genome, causing 'background selection', as well as a single locus at which a polymorphism is maintained, either by frequency-dependent selection or by local selective differences. These balanced polymorphisms induce long coalescence times at linked neutral loci, so that sequence diversity at these loci is enhanced at statistical equilibrium. We study how equilibrium neutral diversity levels are affected by the degree of population subdivision, the presence or absence of background selection, and the level of inbreeding of the population. The simulation results are compared with approximate analytical formulae, assuming the infinite sites neutral model. We discuss how balancing selection can be distinguished from local selection, by determining whether peaks of diversity in the region of the polymorphic locus are seen within or between demes. The width of such diversity peaks is shown to depend on the total species population size, rather than local deme sizes. We show that, with population subdivision, local selection enhances between-deme diversity even at neutral sites distant from the polymorphic locus, producing higher F-ST,, values than with no selection; very high values can be generated at sites close to a selected locus. Background selection also increases F-ST,, mainly because of decreased diversity within populations, which implies that its effects may be distinguishable from those of local selection. Both effects are stronger in selfing than outcrossing populations. Linkage disequilibrium between neutral sites is generated by both balancing and local selection, especially in selfing populations, because of linkage disequilibrium between the neutral sites and the selectively maintained alleles. We discuss how these theoretical results can be related to data on genetic diversity within and between local populations of a species.