Laboratoire de Biométrie et Biologie évolutive, UMR5558, Université Lyon 1, Centre National de la Recherche Scientifique, Villeurbanne, France.
PLoS One. 2011;6(8):e21915. doi: 10.1371/journal.pone.0021915. Epub 2011 Aug 10.
In the plant genus Silene, separate sexes and sex chromosomes are believed to have evolved twice. Silene species that are wholly or largely hermaphroditic are assumed to represent the ancestral state from which dioecy evolved. This assumption is important for choice of outgroup species for inferring the genetic and chromosomal changes involved in the evolution of dioecy, but is mainly based on data from a single locus (ITS). To establish the order of events more clearly, and inform outgroup choice, we therefore carried out (i) multi-nuclear-gene phylogenetic analyses of 14 Silene species (including 7 hermaphrodite or gynodioecious species), representing species from both Silene clades with dioecious members, plus a more distantly related outgroup, and (ii) a BayesTraits character analysis of the evolution of dioecy. We confirm two origins of dioecy within this genus in agreement with recent work on comparing sex chromosomes from both clades with dioecious species. We conclude that sex chromosomes evolved after the origin of Silene and within a clade that includes only S. latifolia and its closest relatives. We estimate that sex chromosomes emerged soon after the split with the ancestor of S. viscosa, the probable closest non-dioecious S. latifolia relative among the species included in our study.
在石竹属植物中，雌雄异株和性染色体被认为分别独立进化了两次。完全或主要是雌雄同体的石竹属物种被认为代表了从雌雄同体进化到雌雄异株的原始状态。这一假设对于推断雌雄异株进化过程中涉及的遗传和染色体变化的外群物种的选择非常重要，但主要基于单个基因座（ITS）的数据。为了更清楚地确定事件的顺序，并为外群选择提供信息，我们因此进行了：（i）对包括 7 种雌雄同体或雌雄异株物种在内的 14 种石竹属物种的多核基因系统发育分析，代表了两个具有雌雄异株成员的石竹属分支中的物种，以及一个更远缘的外群；（ii）对雌雄异株进化的贝叶斯特征分析。我们确认了该属内雌雄异株的两个起源，与最近对两个分支的性染色体与雌雄异株物种进行比较的研究结果一致。我们得出的结论是，性染色体是在石竹属起源之后，并在一个仅包括 S. latifolia 及其最亲近的亲缘种的分支内进化的。我们估计，性染色体是在与 S. viscosa 祖先分裂后不久出现的，S. viscosa 是我们研究中包括的物种中最接近的非雌雄异株 S. latifolia 亲缘种。
