Phylogeny of Salix subgenus Salix s.l. (Salicaceae): delimitation biogeography and reticulate evolution

Background The taxonomy and systematics of Salix subgenus Salix s.l. is difficult. The reliability and evolutionary implications of two important morphological characters (number of stamens, and morphology of bud scales) used in subgeneric classification within Salix remain untested, and a disjunct Old–New World distribution pattern of a main clade of subgenus Salix s.l., revealed by a previous study, lacks a reasonable explanation. To study these questions, we conducted phylogenetic analyses based on 4,688 bp of sequence data from four plastid (rbcL, trnD–T, matK, and atpB–rbcL) and two nuclear markers (ETS and ITS) covering all subgenera of Salix, and all sections of subgenus Salix s.l. Results Subgenus Salix came out as para- or polyphyletic in both nrDNA and plastid trees. The plastid phylogeny successfully resolved relationships among the major clades of Salix, but resolution within subgenus Salix s.l. remained low. Nevertheless, three monophyletic groups were identifiable in subge...

背景 柳属（Salix）广义柳亚属（subgenus Salix s.l.）的分类学（taxonomy）与系统学（systematics）研究难度较大。柳属亚属分类中所采用的两个关键形态特征——雄蕊数量及芽鳞形态——的可靠性及其演化意义尚未得到验证；此外，先前研究揭示的广义柳属柳亚属一个主要分支呈现的新旧世界间断分布模式，仍缺乏合理的解释。为探讨这些问题，我们基于4688 bp的序列数据开展了系统发育分析（phylogenetic analyses），涉及4个质体（plastid）标记（rbcL、trnD–T、matK及atpB–rbcL）与2个核标记（ETS及ITS），覆盖了柳属所有亚属及广义柳属柳亚属的所有组。结果 柳亚属在核核糖体DNA（nrDNA）与质体系统发育树中均表现为并系（para-）或多系（polyphyletic）类群。质体系统发育成功解析了柳属主要分支间的关系，但广义柳属柳亚属内部的分辨率仍较低。不过，在该亚属中可识别出三个单系群（monophyletic groups）……