Mantel Samuel J, Sweigart Andrea L
Department of Genetics, University of Georgia, Athens, GA, 30602, USA.
bioRxiv. 2023 Aug 29:2023.08.05.552095. doi: 10.1101/2023.08.05.552095.
The evolution of postzygotic isolation is thought to be a key step in maintaining species boundaries upon secondary contact, yet the dynamics and persistence of hybrid incompatibilities in sympatric species are not well understood.Here, we explore these issues using genetic mapping in three populations of recombinant inbred lines between naturally hybridizing monkeyflowers and from the sympatric Catherine Creek population.The three founders differ dramatically in admixture history. Comparative genetic mapping also reveals three putative inversions segregating among the founders, two due to admixture. We observe strong, genome-wide transmission ratio distortion, but patterns are highly variable among populations. Some distortion is explained by epistatic selection favoring parental genotypes, but tests of inter-chromosomal linkage disequilibrium also reveal multiple candidate Dobzhansky-Muller incompatibilities. We also map several genetic loci for hybrid fertility, including two interacting pairs coinciding with peaks of distortion.Remarkably, in this limited sample of , we discover abundant segregating variation for hybrid incompatibilities with suggesting this population harbors diverse contributors to postzygotic isolation. Moreover, even with substantial admixture, hybrid incompatibilities between species persist, suggesting postzygotic isolation might be a potent force in maintaining species barriers in this system.
合子后隔离的进化被认为是二次接触时维持物种界限的关键步骤，然而对同域物种中杂种不相容性的动态变化和持续性却了解甚少。在此，我们利用对自然杂交的猴面花之间以及来自同域的凯瑟琳溪种群的三个重组自交系群体进行基因定位来探究这些问题。这三个亲本在混合历史上有显著差异。比较基因定位还揭示了在亲本之间分离的三个假定倒位，其中两个是由于混合导致的。我们观察到全基因组范围内强烈的传递率扭曲，但不同群体间的模式差异很大。部分扭曲可由有利于亲本基因型的上位性选择来解释，但染色体间连锁不平衡测试也揭示了多个候选的多布赞斯基 - 穆勒不相容性。我们还定位了几个影响杂种育性的基因座，包括两对相互作用的基因座，它们与扭曲峰值重合。值得注意的是，在这个有限的样本中，我们发现了丰富的杂种不相容性分离变异，这表明该种群包含了对合子后隔离有多种贡献的因素。此外，即使存在大量混合，两个物种之间的杂种不相容性仍然存在，这表明合子后隔离可能是在这个系统中维持物种屏障的一股强大力量。
