Seasonally fluctuating selection can maintain polymorphism at many loci via segregation lift.
Seasonally fluctuating selection can maintain polymorphism at many loci via segregation lift.
复制标题
季节性波动的选择可以通过分离提升维持许多位点的多态性。
DOI：
10.1073/pnas.1702994114
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发表时间：
2017
影响因子：
11.1
通讯作者：
Petrov,DmitriA
中科院分区：
文献类型：
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作者：
Wittmann,MeikeJ;Bergland,AlanO;Feldman,MarcusW;Schmidt,PaulS;Petrov,DmitriA
大多数自然种群受到温度、降雨量或资源可用性的季节性变化的影响。季节性波动的选择可能会对维持种群的遗传多态性做出很大贡献。然而，以前的理论表明，多位点多态性的条件是限制性的。在这里，我们探讨了一类更一般的模型与多位点的季节性波动选择二倍体。在这些模型中，多位点基因型映射到健身分两步。第一个映射是加性的基因座和占杂合和纯合基因座的相对贡献，即显性。第二步使用非线性适应度函数来解释选择和上位性的强度。使用数学分析和基于个人的模拟，我们表明，稳定的多态性在许多位点是可能的，如果目前有利的等位基因是足够的优势。这种一般的机制，我们称之为“隔离升降机”，需要季节性变化的优势，一种现象，可能会出现自然的情况下，拮抗多效性和季节性变化的相对重要性的性状的健身。分离升降机工程最好的递减回报上位性，是不受遗传负荷的问题，是强大的跨基因座和季节的参数差异。在分离解除下，基因座可以表现出明显的季节性等位基因频率波动，但波动往往很小，难以检测。未来工作的一个重要方向是正式测试隔离电梯的经验数据，并量化其对维持自然群体的遗传变异的贡献。
Most natural populations are affected by seasonal changes in temperature, rainfall, or resource availability. Seasonally fluctuating selection could potentially make a large contribution to maintaining genetic polymorphism in populations. However, previous theory suggests that the conditions for multilocus polymorphism are restrictive. Here, we explore a more general class of models with multilocus seasonally fluctuating selection in diploids. In these models, the multilocus genotype is mapped to fitness in two steps. The first mapping is additive across loci and accounts for the relative contributions of heterozygous and homozygous loci—that is, dominance. The second step uses a nonlinear fitness function to account for the strength of selection and epistasis. Using mathematical analysis and individual-based simulations, we show that stable polymorphism at many loci is possible if currently favored alleles are sufficiently dominant. This general mechanism, which we call “segregation lift,” requires seasonal changes in dominance, a phenomenon that may arise naturally in situations with antagonistic pleiotropy and seasonal changes in the relative importance of traits for fitness. Segregation lift works best under diminishing-returns epistasis, is not affected by problems of genetic load, and is robust to differences in parameters across loci and seasons. Under segregation lift, loci can exhibit conspicuous seasonal allele-frequency fluctuations, but often fluctuations may be small and hard to detect. An important direction for future work is to formally test for segregation lift in empirical data and to quantify its contribution to maintaining genetic variation in natural populations.