Data from: Genetic diversity and multiple origins of polyploid Atriplex nummularia Lindl. (Chenopodiaceae).

Few studies have described the genetic diversity within and between populations of polyploid plant species despite the general acceptance of the importance of polyploidy in plant diversification and speciation. The genus Atriplex has a complex evolutionary history in Australia that has included polyploidy and hybridization among perennial forms. The octoploid, dioecious species Atriplex nummularia is proposed to have evolved from an octoploid ancestor in the coastal semi-arid fringe of south-western Australia, and to have spread east and diversified into taxa which occupy edaphically different habitats. Despite interest in the diversification of the genus, and the ecological and economic importance of A. nummularia, there are no descriptions of the genetic structure of the species. Nuclear microsatellite markers and principal coordinate analysis, analysis of molecular variance, Bayesian and phenetic analyses were used to investigate the diversity and taxonomic relationships of two common subspecies of A. nummularia. Genetic diversity was high overall (A = 509, A′ = 42.4, Ho = 0.824, H′ = 2.8), but values were significantly lower in the western subspecies, A. nummularia ssp. spathulata. As in other outbreeding, perennial species, most of the genetic diversity was within populations (FST = 0.125). Clear divergence of subspecies was evident in principal coordinate analysis, neighbor-joining and Bayesian clustering analyses and the differentiation of populations was very low within subspecies (FSC = 0.048). These findings support the taxonomic separation of the two subspecies. Clustering patterns based on Bayesian analyses suggested that the polyploid subspecies of A. nummularia have multiple origins.

尽管学界已普遍认可多倍化（polyploidy）在植物分异与物种形成中的关键作用，但目前针对多倍体植物物种种群内及种群间遗传多样性的研究仍相对匮乏。滨藜属（Atriplex）在澳大利亚拥有极为复杂的演化历史，其间既发生过多倍化事件，也存在多年生类群间的杂交过程。八倍体（octoploid）雌雄异株（dioecious）物种圆叶滨藜（Atriplex nummularia）被推测由澳大利亚西南部沿海半干旱边缘带的八倍体祖先演化而来，随后向东扩散并分化为占据不同土壤生境的多个类群。尽管学界对滨藜属的物种分异过程、以及圆叶滨藜的生态与经济价值均存在广泛关注，但目前尚无针对该物种遗传结构的系统性研究报道。本研究采用核微卫星标记（nuclear microsatellite markers）、主坐标分析（principal coordinate analysis）、分子方差分析（analysis of molecular variance）、贝叶斯分析及表型分析，对圆叶滨藜的两个常见亚种的遗传多样性与分类学关系展开探究。整体而言，该物种的遗传多样性水平较高（等位基因数A=509，标准化等位基因丰富度A′=42.4，观测杂合度Ho=0.824，香农多样性指数H′=2.8），但西部亚种匙叶圆叶滨藜（A. nummularia ssp. spathulata）的遗传多样性水平显著更低。与其他异交多年生植物类群一致，该物种的绝大多数遗传变异存在于种群内部（总群体遗传分化系数FST=0.125）。主坐标分析、邻接树法与贝叶斯聚类分析均清晰显示出两个亚种的遗传分化，且亚种内种群间的遗传分化程度极低（亚种内种群分化系数FSC=0.048）。上述研究结果支持将圆叶滨藜的两个亚种划分为独立分类单元。基于贝叶斯分析的聚类结果还表明，圆叶滨藜的多倍体亚种存在多次独立起源事件。