Polygenic variation maintained by balancing selection: pleiotropy, sex-dependent allelic effects and G x E interactions.
Polygenic variation maintained by balancing selection: pleiotropy, sex-dependent allelic effects and G x E interactions.
复制标题
DOI：
10.1534/genetics.166.2.1053
复制
发表时间：
2004-02
期刊：
影响因子：
3.3
通讯作者：
M. Turelli;N. H. Barton
中科院分区：
文献类型：
--
作者：
M. Turelli;N. H. Barton
我们研究了三种基于选择的方案，提出了保持多基因变异：多效性平衡选择，G x E相互作用（与空间或时间变化的等位基因效应），和性别依赖的等位基因效应。每个分析假设一个加性多基因性状与n双等位基因位点下稳定选择。我们允许基因座有不同的影响，并考虑平衡，在该群体的平均值偏离稳定选择的最佳。在弱选择下，每个模型产生基本相同的近似等位基因频率动态。只有在平衡选择的强度超过稳定选择的有效强度的基因座上，才能在多效性平衡选择下保持变异。此外，对于所有模型，多态性要求群体均值足够接近最优值，使得定向选择不会压倒平衡选择。这种平衡允许许多同时稳定的平衡，我们探讨它们的属性数值。空间和时间的G x E可以保持在基因座的变化，其中的变异系数（跨环境）的替代效果超过一个临界值大于1。临界值取决于不同位点上替代效应之间的相关性。对于大的正相关性（例如，rho（ij）2>3/4），甚至等位基因效应的极端波动也不能维持变异。令人惊讶的是，这种相关性的约束意味着性别依赖的等位基因效应不能维持多基因变异。我们提出的数值结果，支持我们的分析近似，并讨论我们的结果与相关数据和替代方差保持机制。
We investigate three alternative selection-based scenarios proposed to maintain polygenic variation: pleiotropic balancing selection, G x E interactions (with spatial or temporal variation in allelic effects), and sex-dependent allelic effects. Each analysis assumes an additive polygenic trait with n diallelic loci under stabilizing selection. We allow loci to have different effects and consider equilibria at which the population mean departs from the stabilizing-selection optimum. Under weak selection, each model produces essentially identical, approximate allele-frequency dynamics. Variation is maintained under pleiotropic balancing selection only at loci for which the strength of balancing selection exceeds the effective strength of stabilizing selection. In addition, for all models, polymorphism requires that the population mean be close enough to the optimum that directional selection does not overwhelm balancing selection. This balance allows many simultaneously stable equilibria, and we explore their properties numerically. Both spatial and temporal G x E can maintain variation at loci for which the coefficient of variation (across environments) of the effect of a substitution exceeds a critical value greater than one. The critical value depends on the correlation between substitution effects at different loci. For large positive correlations (e.g., rho(ij)2>3/4), even extreme fluctuations in allelic effects cannot maintain variation. Surprisingly, this constraint on correlations implies that sex-dependent allelic effects cannot maintain polygenic variation. We present numerical results that support our analytical approximations and discuss our results in connection to relevant data and alternative variance-maintaining mechanisms.