CNRS, ECOBIO (Ecosystèmes, biodiversité, évolution), University of Rennes 1, UMR 6553, Rennes, France.
Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala, 752 36, Sweden.
Evolution. 2021 May;75(5):1011-1029. doi: 10.1111/evo.14194. Epub 2021 Apr 5.
Self-fertilization commonly occurs in hermaphroditic species, either occasionally or as the main reproductive mode. It strongly affects the genetic functioning of a population by increasing homozygosity and genetic drift and reducing the effectiveness of recombination. Balancing selection is a form of selection that maintains polymorphism, which has been extensively studied in outcrossing species. Yet, despite recent developments, the analysis of balancing selection in partially selfing species is limited to specific cases and a general treatment is still lacking. In particular, it is unclear whether selfing globally reduced the efficacy of balancing selection as in the well-known case of overdominance. I provide a unifying framework, quantify how selfing affects the maintenance of polymorphism and the efficacy of the different form of balancing selection, and show that they can be classified into two main categories: overdominance-like selection (including true overdominance, selection variable in space and time, and antagonistic selection), which is strongly affected by selfing, and negative frequency dependent selection, which is barely affected by selfing, even at multiple loci. I also provide simple analytical results for all cases under the assumption of weak selection. This framework provides theoretical background to analyze the genomic signature of balancing selection in partially selfing species. It also sheds new light on the evolution of selfing species, including the evolution of selfing syndrome, the interaction with pathogens, and the evolutionary fate of selfing lineages.
自体受精通常发生在雌雄同体的物种中，或者偶尔发生，或者作为主要的生殖方式。它通过增加同型性和遗传漂变，减少重组的有效性，强烈影响种群的遗传功能。平衡选择是一种保持多态性的选择形式，在外交物种中得到了广泛研究。然而，尽管最近取得了一些进展，但对部分自交物种中平衡选择的分析仅限于特定情况，仍缺乏一般性的处理方法。特别是，自交是否像众所周知的超显性情况那样，全局降低平衡选择的效果还不清楚。我提供了一个统一的框架，量化了自交如何影响多态性的维持和不同形式的平衡选择的效果，并表明它们可以分为两类：类似于超显性的选择（包括真正的超显性、空间和时间上可变的选择和拮抗选择），受自交影响很大，以及负频率依赖选择，受自交影响很小，即使在多个位点也是如此。我还在弱选择的假设下，为所有情况提供了简单的分析结果。这个框架为分析部分自交物种中平衡选择的基因组特征提供了理论背景。它也为自交物种的进化提供了新的视角，包括自交综合征的进化、与病原体的相互作用以及自交谱系的进化命运。
