Department of Ecology and Genetics, Evolutionary Biology Center, Uppsala University, Uppsala, Sweden.
Mol Ecol. 2018 Oct;27(19):3889-3904. doi: 10.1111/mec.14562. Epub 2018 Apr 29.
The evolution of reproductive barriers and their underlying genetic architecture is of central importance for the formation of new species. Reproductive barriers can be controlled either by few large-effect loci suggesting strong selection on key traits, or by many small-effect loci, consistent with gradual divergence or with selection on polygenic or multiple traits. Genetic coupling between reproductive barrier loci further promotes divergence, particularly divergence with ongoing gene flow. In this study, we investigated the genetic architectures of ten morphological, phenological and life history traits associated with reproductive barriers between the hybridizing sister species Silene dioica and S. latifolia; both are dioecious with XY-sex determination. We used quantitative trait locus (QTL) mapping in two reciprocal F crosses. One to six QTLs per trait, including nine major QTLs (PVE > 20%), were detected on 11 of the 12 linkage groups. We found strong evidence for coupling of QTLs for uncorrelated traits and for an important role of sex chromosomes in the genetic architectures of reproductive barrier traits. Unexpectedly, QTLs detected in the two F crosses differed largely, despite limited phenotypic differences between them and sufficient statistical power. The widely dispersed genetic architectures of traits associated with reproductive barriers suggest gradual divergence or multifarious selection. Coupling of the underlying QTLs likely promoted divergence with gene flow in this system. The low congruence of QTLs between the two crosses further points to variable and possibly redundant genetic architectures of traits associated with reproductive barriers, with important implications for the evolutionary dynamics of divergence and speciation.
生殖隔离的进化及其潜在的遗传结构对于新物种的形成至关重要。生殖隔离可以由少数几个大效应位点控制，这些位点表明对关键特征的强烈选择，也可以由许多小效应位点控制，这与渐进性分歧或多基因或多个特征的选择一致。生殖隔离位点之间的遗传耦合进一步促进了分歧，特别是在有持续基因流的情况下。在这项研究中，我们研究了与杂交姐妹种拟南芥（Silene dioica）和 S. latifolia 之间生殖隔离相关的十个形态学、物候学和生活史特征的遗传结构；这两个种都是雌雄异株，具有 XY 性别决定。我们在两个相互的 F 杂交中使用了数量性状位点（QTL）作图。每个性状检测到一个到六个 QTL，包括九个主要 QTL（PVE > 20%），分布在 12 个连锁群中的 11 个上。我们发现，不相关性状的 QTL 之间存在强烈的耦合，以及性染色体在生殖隔离性状的遗传结构中起着重要作用。出乎意料的是，尽管两个 F 杂交之间的表型差异有限，且具有足够的统计能力，但在两个 F 杂交中检测到的 QTL 差异很大。与生殖隔离相关的性状的广泛分散的遗传结构表明渐进性分歧或多种选择。在这个系统中，潜在 QTL 的耦合可能促进了与基因流的分歧。两个杂交之间 QTL 的低一致性进一步表明与生殖隔离相关的性状的遗传结构具有可变性和可能的冗余性，这对分歧和物种形成的进化动态具有重要意义。
