Lauron-Moreau Aurélien, Pitre Frédéric E, Argus George W, Labrecque Michel, Brouillet Luc
Institut de recherche en biologie végétale, Université de Montréal, Montréal, QC, Canada.
Canadian Museum of Nature, Ottawa, Canada.
PLoS One. 2015 Apr 16;10(4):e0121965. doi: 10.1371/journal.pone.0121965. eCollection 2015.
Salix L. is the largest genus in the family Salicaceae (450 species). Several classifications have been published, but taxonomic subdivision has been under continuous revision. Our goal is to establish the phylogenetic structure of the genus using molecular data on all American willows, using three DNA markers. This complete phylogeny of American willows allows us to propose a biogeographic framework for the evolution of the genus. Material was obtained for the 122 native and introduced willow species of America. Sequences were obtained from the ITS (ribosomal nuclear DNA) and two plastid regions, matK and rbcL. Phylogenetic analyses (parsimony, maximum likelihood, Bayesian inference) were performed on the data. Geographic distribution was mapped onto the tree. The species tree provides strong support for a division of the genus into two subgenera, Salix and Vetrix. Subgenus Salix comprises temperate species from the Americas and Asia, and their disjunction may result from Tertiary events. Subgenus Vetrix is composed of boreo-arctic species of the Northern Hemisphere and their radiation may coincide with the Quaternary glaciations. Sixteen species have ambiguous positions; genetic diversity is lower in subg. Vetrix. A molecular phylogeny of all species of American willows has been inferred. It needs to be tested and further resolved using other molecular data. Nonetheless, the genus clearly has two clades that have distinct biogeographic patterns.
柳属（Salix L.）是杨柳科中最大的属（有450个物种）。已经发表了几种分类法，但分类细分一直在不断修订。我们的目标是利用所有美洲柳树的分子数据，使用三种DNA标记来建立该属的系统发育结构。这一完整的美洲柳树系统发育图使我们能够为该属的进化提出一个生物地理框架。获取了美洲122种原生和引入柳树物种的材料。序列取自ITS（核糖体核DNA）以及两个质体区域matK和rbcL。对数据进行了系统发育分析（简约法、最大似然法、贝叶斯推断）。将地理分布绘制到树上。物种树为将该属划分为两个亚属，即柳亚属（Salix）和紫柳亚属（Vetrix）提供了有力支持。柳亚属包括来自美洲和亚洲的温带物种，它们的间断分布可能是第三纪事件导致的。紫柳亚属由北半球的寒北极物种组成，它们的辐射可能与第四纪冰川作用同时发生。16个物种的位置不明确；紫柳亚属的遗传多样性较低。已经推断出了所有美洲柳树物种的分子系统发育图。需要使用其他分子数据对其进行检验并进一步解析。尽管如此，该属显然有两个具有不同生物地理模式的进化枝。
