背景回顧：About 15,000 angiosperm species (∼6%) have separate sexes, a phenomenon known as dioecy. Why dioecious taxa are so rare is still an open question.
已有假設：Early work reported lower species richness in dioecious compared to non-dioecious sister clades, raising the hypothesis that dioecy may be an evolutionary dead-end.
存在問題：This hypothesis has been recently challenged by macro-evolutionary analyses that detected no or even positive effect of dioecy on diversification.
提出問題：However, the possible genetic consequences of dioecy at the population level, which could drive the long-term fate of dioecious lineages, have not been tested so far.
主要研究：Here, we used a population genomics approach in the Silene genus to look for possible effects of dioecy, especially for potential evidence of evolutionary handicaps of dioecy underlying the dead-end hypothesis.
研究材料：We collected individual-based RNA-seq data from several populations in 13 closely related species with different sexual systems: seven dioecious, three hermaphroditic and three gynodioecious species.
初步結果：We show that dioecy is associated with increased genetic diversity, as well as higher selection efficacy both against deleterious mutations and for beneficial mutations.
夯實結果：The results hold after controlling for phylogenetic inertia, differences in species census population sizes and geographic ranges.
結論：We conclude that dioecious Silene speciesneither show signs of increased mutational load nor genetic evidence for extinction risk.
討論：We discuss these observations in the light of the possible demographic differences between dioecious and self-compatible hermaphroditic species and how this could be related to alternatives to the dead-end hypothesis to explain the rarity of dioecy.