Department of Mathematics, University of Vienna, 1090 Vienna, Austria.
Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal.
Philos Trans R Soc Lond B Biol Sci. 2020 Aug 31;375(1806):20190532. doi: 10.1098/rstb.2019.0532. Epub 2020 Jul 13.
Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky-Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that many incipient species may initially face. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.
基因流往往会阻碍遗传分歧的积累。在这里，我们确定了通过基因流连接的两个种群的合子后生殖隔离进化的极限。我们考虑了两种创建和维持遗传障碍的选择机制：由于对移民的选择，局部适应导致初期物种之间的分歧，而 Dobzhansky-Muller 不相容性（DMIs）通过对杂种的选择来加强遗传障碍。特别是，我们对在有限的局部适应量下障碍的最大强度感兴趣，这是许多初期物种可能最初面临的挑战。我们首先证实，对于经典的双基因座 DMIs，最大的局部适应量确实是遗传障碍强度的极限。然而，对于三个或更多的基因座和隐性上位性，这个极限不再成立。具体来说，我们确定了一个由三个相互作用的突变组成的最小配置，足以赋予强烈的生殖隔离。本文是“迈向物种形成的完成：超越第一道障碍的生殖隔离进化”主题特刊的一部分。
