Data from: Disentangling the effects of mating systems and mutation rates on cytoplamic diversity in gynodioecious Silene nutans and dioecious Silene otites

Many flowering plant species exhibit a variety of distinct sexual morphs, the two most common cases being the co- occurrence of females and males (dioecy) or the co-occurrence of hermaphrodites and females (gynodioecy). In this study we compared DNA sequence variability of the three genomes (nuclear, mitochondrial and chloroplastic) of a gynodioecious species, Silene nutans, with that of a closely related dioecious species, Silene otites. In the light of theoretical models, we expect cytoplasmic diversity to differ between the two species due to the selective dynamics that acts on cytoplasmic genomes in gynodioecious species: under an epidemic scenario, the gynodioecious species is expected to exhibit lower cytoplasmic diversity than the dioecious species, while the opposite is expected in the case of balancing selection maintaining sterility cytoplasms in the gynodioecious species. We found no difference between the species for nuclear gene diversity, but, for the cytoplasmic loci, the gynodioecious S. nutans had more haplotypes, and higher nucleotide diversity, than the dioecious relative, S. otites, even though the latter has a relatively high rate of mitochondrial synonymous substitutions, and therefore presumably a higher mutation rate. Therefore, since the mitochondrial mutation rate cannot account for the higher cytoplasmic diversity found in S. nutans, our findings support the hypothesis that gynodioecy in S. nutans has been maintained by balancing selection rather than by epidemic-like dynamics.诸多显花植物物种展现出多种截然不同的性形态，其中两种最为常见的类型分别为雌性与雄性个体共存的雌雄异株（dioecy），以及雌雄同株个体与雌性个体共存的雌全异株（gynodioecy）。本研究针对一种雌全异株物种垂花麦瓶草（Silene nutans）与亲缘关系紧密的雌雄异株物种奥蒂麦瓶草（Silene otites）的三类基因组——核基因组、线粒体基因组与叶绿体基因组的DNA序列变异度展开了对比分析。依据理论模型，我们推测两类物种的细胞质多样性存在差异，这源于作用于雌全异株物种细胞质基因组的选择动力学：在流行传播场景下，雌全异株物种的细胞质多样性预计低于雌雄异株物种；而当平衡选择维持雌全异株物种的不育细胞质时，二者的细胞质多样性则会呈现相反的趋势。研究结果显示，两类物种的核基因多样性并无显著差异；但对于细胞质位点而言，尽管奥蒂麦瓶草（S. otites）的线粒体同义替换率相对较高，推测其突变率也更高，但雌全异株的垂花麦瓶草（S. nutans）仍比其雌雄异株近缘物种拥有更多的单倍型与更高的核苷酸多样性。因此，鉴于线粒体突变率无法解释垂花麦瓶草（S. nutans）较高的细胞质多样性，本研究结果支持如下假说：垂花麦瓶草的雌全异株性状是由平衡选择所维持，而非类似流行传播的动力学机制所维持。