Gavrilets S, de Jong G
N.I. Vavilov Institute of General Genetics, Moscow, Russia.
Genetics. 1993 Jun;134(2):609-25. doi: 10.1093/genetics/134.2.609.
We show that in polymorphic populations many polygenic traits pleiotropically related to fitness are expected to be under apparent "stabilizing selection" independently of the real selection acting on the population. This occurs, for example, if the genetic system is at a stable polymorphic equilibrium determined by selection and the nonadditive contributions of the loci to the trait value either are absent, or are random and independent of those to fitness. Stabilizing selection is also observed if the polygenic system is at an equilibrium determined by a balance between selection and mutation (or migration) when both additive and nonadditive contributions of the loci to the trait value are random and independent of those to fitness. We also compare different viability models that can maintain genetic variability at many loci with respect to their ability to account for the strong stabilizing selection on an additive trait. Let Vm be the genetic variance supplied by mutation (or migration) each generation, Vg be the genotypic variance maintained in the population, and n be the number of the loci influencing fitness. We demonstrate that in mutation (migration)-selection balance models the strength of apparent stabilizing selection is order Vm/Vg. In the overdominant model and in the symmetric viability model the strength of apparent stabilizing selection is approximately 1/(2n) that of total selection on the whole phenotype. We show that a selection system that involves pairwise additive by additive epistasis in maintaining variability can lead to a lower genetic load and genetic variance in fitness (approximately 1/(2n) times) than an equivalent selection system that involves overdominance. We show that, in the epistatic model, the apparent stabilizing selection on an additive trait can be as strong as the total selection on the whole phenotype.
我们表明，在多态性群体中，许多与适合度呈多效性相关的多基因性状预计会处于明显的“稳定选择”之下，而与作用于该群体的实际选择无关。例如，如果遗传系统处于由选择决定的稳定多态平衡状态，并且基因座对性状值的非加性贡献不存在，或者是随机的且与对适合度的贡献无关，就会出现这种情况。当基因座对性状值的加性和非加性贡献都是随机的且与对适合度的贡献无关时，如果多基因系统处于由选择与突变（或迁移）之间的平衡所决定的平衡状态，也会观察到稳定选择。我们还比较了不同的生存力模型，这些模型在维持多个基因座的遗传变异性方面，就其解释对加性性状的强稳定选择的能力而言。设Vm为每代由突变（或迁移）提供的遗传方差，Vg为群体中维持的基因型方差，n为影响适合度的基因座数量。我们证明，在突变（迁移） - 选择平衡模型中，表观稳定选择的强度为Vm/Vg量级。在超显性模型和对称生存力模型中，表观稳定选择的强度约为对整个表型的总选择强度的1/(2n)。我们表明，一个在维持变异性方面涉及加性×加性上位性的选择系统，与一个涉及超显性的等效选择系统相比，可导致更低的遗传负荷和适合度方面的遗传方差（约为1/(2n)倍）。我们表明，在上位性模型中，对加性性状的表观稳定选择可以与对整个表型的总选择一样强。
