Merilä J, Sheldon B C
Department of Population Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18d, SE-752 36 Uppsala, Sweden.
Heredity (Edinb). 1999 Aug;83 ( Pt 2):103-9. doi: 10.1046/j.1365-2540.1999.00585.x.
Comparative studies of the genetic architecture of different types of traits were initially prompted by the expectation that traits under strong directional selection (fitness traits) should have lower levels of genetic variability than those mainly under weak stabilizing selection (nonfitness traits). Hence, early comparative studies revealing lower heritabilities of fitness than nonfitness traits were first framed in terms of giving empirical support for this prediction, but subsequent treatments have effectively reversed this view. Fitness traits seem to have higher levels of additive genetic variance than nonfitness traits - an observation that has been explained in terms of the larger number loci influencing fitness as compared to nonfitness traits. This hypothesis about the larger functional architecture of fitness than nonfitness traits is supported by their higher mutational variability, which is hard to reconcile without evoking capture of mutational variability over many loci. The lower heritabilities of fitness than nonfitness traits, despite the higher additive genetic variance of the former, occur because of their higher residual variances. Recent comparative studies of dominance contributions for different types of traits, together with theoretical predictions and a large body of indirect evidence, suggest an important role of dominance variance in determining levels of residual variance for fitness-traits. The role of epistasis should not be discounted either, since a large number of loci increases the potential for epistatic interactions, and epistasis is strongly implicated in hybrid breakdown.
不同类型性状的遗传结构比较研究最初是由这样一种预期所推动的，即受强定向选择的性状（适应度性状）的遗传变异性水平应低于主要受弱稳定选择的性状（非适应度性状）。因此，早期揭示适应度性状的遗传力低于非适应度性状的比较研究最初是从为这一预测提供实证支持的角度来阐述的，但随后的研究有效地扭转了这一观点。适应度性状似乎比非适应度性状具有更高水平的加性遗传方差——这一观察结果已根据与非适应度性状相比影响适应度的基因座数量更多来解释。关于适应度性状的功能结构比非适应度性状更大的这一假设，得到了它们更高的突变变异性的支持，若不考虑在多个基因座上对突变变异性的捕获，这很难解释。尽管适应度性状的加性遗传方差较高，但其遗传力低于非适应度性状，是因为它们的残差方差较高。最近对不同类型性状的显性贡献的比较研究，连同理论预测和大量间接证据，表明显性方差在决定适应度性状的残差方差水平方面起着重要作用。上位性的作用也不应被忽视，因为大量的基因座增加了上位性相互作用的可能性，而且上位性与杂种衰败密切相关。
