Data from: Selfish evolution of cytonuclear hybrid incompatibility in Mimulus

Intraspecific coevolution between selfish elements and suppressors may promote interspecific hybrid incompatibility, but evidence of this process is rare. Here, we use genomic data to test alternative models for the evolution of cytonuclear hybrid male sterility in Mimulus. In hybrids between Iron Mountain (IM) Mimulus guttatus × Mimulus nasutus, two tightly linked M. guttatus alleles (Rf1/Rf2) each restore male fertility by suppressing a local mitochondrial male-sterility gene (IM-CMS). Unlike neutral models for the evolution of hybrid incompatibility loci, selfish evolution predicts that the Rf alleles experienced strong selection in the presence of IM-CMS. Using whole-genome sequences, we compared patterns of population-genetic variation in Rf at IM to a neighbouring population that lacks IM-CMS. Consistent with local selection in the presence of IM-CMS, the Rf region shows elevated FST, high local linkage disequilibrium and a distinct haplotype structure at IM, but not at Cone Peak (CP), suggesting a recent sweep in the presence of IM-CMS. In both populations, Rf2 exhibited lower polymorphism than other regions, but the low-diversity outliers were different between CP and IM. Our results confirm theoretical predictions of ubiquitous cytonuclear conflict in plants and provide a population-genetic mechanism for the evolution of a common form of hybrid incompatibility.自私遗传元件与抑制因子之间的种内协同进化，或可推动种间杂交不相容性的演化，但目前支持该过程的实证证据较为匮乏。本研究借助基因组数据，对沟酸浆属（Mimulus）内核质互作型杂交雄性不育的演化假说展开验证。在铁山（Iron Mountain, IM）种群斑点沟酸浆（Mimulus guttatus）与纳斯图特沟酸浆（Mimulus nasutus）的杂交后代中，两个紧密连锁的斑点沟酸浆等位基因Rf1、Rf2均可通过抑制局部线粒体雄性不育基因IM-CMS，恢复杂交后代的雄性育性。与杂交不相容位点演化的中性模型不同，自私演化理论预测：在IM-CMS存在的情况下，Rf等位基因曾经历强烈的正向选择。本研究利用全基因组序列数据，对比了铁山种群与另一个缺乏IM-CMS的邻近种群——锥峰（Cone Peak, CP）——中Rf位点的群体遗传变异模式。这与IM-CMS存在时的局部选择效应相符：铁山种群的Rf区域呈现出升高的FST值、显著的局部连锁不平衡以及独特的单倍型结构，而锥峰种群则无此特征，提示在IM-CMS存在的情况下曾发生过一次近期的选择性清除事件。在两个种群中，Rf2的多态性水平均低于其他基因组区域，但CP与IM种群间的低多样性异常位点存在显著差异。本研究结果证实了植物中普遍存在核质冲突的理论预测，并为一类常见杂交不相容性的演化提供了群体遗传层面的解释机制。