Centre d'Ecologie Fonctionnelle et Evolutive, 34293 Montpellier, France.
Genetics. 2011 Nov;189(3):923-37. doi: 10.1534/genetics.111.132944. Epub 2011 Sep 2.
Deleterious mutations tend to be recessive. Several theories, notably those of Fisher (based on selection) and Wright (based on metabolism), have been put forward to explain this pattern. Despite a long-lasting debate, the matter remains unresolved. This debate has focused on the average dominance of mutations. However, we also know very little about the distribution of dominance coefficients among mutations, and about its variation across environments. In this article we present a new approach to predicting this distribution. Our approach is based on a phenotypic fitness landscape model. First, we show that under a very broad range of conditions (and environments), the average dominance of mutation of small effects should be approximately one-quarter as long as adaptation of organisms to their environment can be well described by stabilizing selection on an arbitrary set of phenotypic traits. Second, the theory allows predicting the whole distribution of dominance coefficients among mutants. Because it provides quantitative rather than qualitative predictions, this theory can be directly compared to data. We found that its prediction on mean dominance (average dominance close to 0.25) agreed well with the data, based on a meta-analysis of dominance data for mildly deleterious mutations. However, a simple landscape model does not account for the dominance of mutations of large effects and we provide possible extension of the theory for this class of mutations. Because dominance is a central parameter for evolutionary theory, and because these predictions are quantitative, they set the stage for a wide range of applications and further empirical tests.
有害突变往往是隐性的。Fisher(基于选择)和 Wright(基于代谢)等理论都提出了解释这种模式的理论。尽管存在长期的争论,但这个问题仍然没有解决。这场争论主要集中在突变的平均显性上。然而,我们对突变的显性系数分布及其在不同环境中的变化也知之甚少。在本文中,我们提出了一种预测这种分布的新方法。我们的方法基于表型适应度景观模型。首先,我们表明,在非常广泛的条件(和环境)下,小效应突变的平均显性应该大约是生物体适应环境的稳定性选择对任意一组表型性状的四分之一。其次,该理论可以预测突变体之间显性系数的整个分布。因为它提供了定量而不是定性的预测,所以这个理论可以直接与数据进行比较。我们发现,根据对轻度有害突变的显性数据的荟萃分析,其对平均显性的预测(接近 0.25 的平均显性)与数据吻合得很好。然而,简单的景观模型并不能解释大效应突变的显性,我们为这一类突变提供了理论的可能扩展。因为显性是进化理论的一个核心参数,而且这些预测是定量的,所以它们为广泛的应用和进一步的经验测试奠定了基础。