Gavrilets S, Hastings A
Division of Environmental Studies, University of California, Davis 95616.
Genetics. 1993 May;134(1):377-86. doi: 10.1093/genetics/134.1.377.
We study a two locus model with additive contributions to the phenotype to explore the relationship between stabilizing selection and recombination. We show that if the double heterozygote has the optimum phenotype and the contributions of the loci to the trait are different, then any symmetric stabilizing selection fitness function can maintain genetic variability provided selection is sufficiently strong relative to linkage. We present results of a detailed analysis of the quadratic fitness function which show that selection need not be extremely strong relative to recombination for the polymorphic equilibria to be stable. At these polymorphic equilibria the mean value of the trait, in general, is not equal to the optimum phenotype, there exists a large level of negative linkage disequilibrium which "hides" additive genetic variance, and different equilibria can be stable simultaneously. We analyze dependence of different characteristics of these equilibria on the location of optimum phenotype, on the difference in allelic effect, and on the strength of selection relative to recombination. Our overall result that stabilizing selection does not necessarily eliminate genetic variability is compatible with some experimental results where the lines subject to strong stabilizing selection did not have significant reductions in genetic variability.
我们研究了一个对表型有累加效应的双基因座模型，以探究稳定选择与重组之间的关系。我们表明，如果双杂合子具有最优表型且基因座对性状的贡献不同，那么只要相对于连锁而言选择足够强，任何对称的稳定选择适应度函数都能维持遗传变异性。我们给出了对二次适应度函数详细分析的结果，这些结果表明，对于多态平衡的稳定而言，选择相对于重组不一定需要极强。在这些多态平衡中，性状的平均值通常不等于最优表型，存在大量的负连锁不平衡，它“隐藏”了加性遗传方差，并且不同的平衡可以同时稳定。我们分析了这些平衡的不同特征对最优表型位置、等位基因效应差异以及相对于重组的选择强度的依赖性。我们的总体结果，即稳定选择不一定消除遗传变异性，与一些实验结果相符，在这些实验中，受到强稳定选择的品系在遗传变异性上并没有显著降低。
