Data from: Molecular phylogenetics and the evolution of fruit and leaf morphology of Dichaea (Orchidaceae: Zygopetalinae)

BACKGROUND AND AIMS: The orchid genus Dichaea, with over 100 species found throughout the neotropics, is easily recognized by distichous leaves on long stems without pseudobulbs and flowers with infrastigmatic ligules. The genus has previously been divided into four sections based primarily on presence of ovary bristles and a foliar abscission layer. The aim of this work is to use DNA sequence data to estimate phylogenetic relationships within Dichaea and map the distribution of major morphological characters that have been used to delimit subgenera/sections. METHODS: Sequence data for the nuclear ribosomal internal transcribed spacers and plastid matK, trnL intron, trnL-F spacer and ycf1 for 67 ingroup and seven outgroup operational taxonomic units were used to estimate phylogenetic relationships within Dichaea. Taxa from each of the four sections were sampled, with the greatest representation from section Dichaea, the most diverse and taxonomically puzzling group. KEY RESULTS: Molecular data and morphology support monophyly of Dichaea. Results indicate that section Dichaeopsis is polyphyletic and based on symplesiomorphies, including deciduous leaves and smooth ovaries that are widespread in Zygopetalinae. There are at least three well-supported clades within section Dichaeopsis. Section Pseudodichaea is monophyletic and defined by setose ovaries and leaves with an abscission layer. Sections Dichaea and Dichaeastrum are monophyletic and defined by pendent habit and persistent leaves. Section Dichaeastrum, distinguished from section Dichaea primarily by a glabrous ovary, is potentially polyphyletic. CONCLUSIONS: The leaf abscission layer was lost once, occurring only in the derived sections Dichaea and Dichaeastrum. The setose fruit is a more homoplasious character with several losses and gains within the genus. We propose an informal division of the genus based upon five well-supported clades.研究背景与目的：兰属（Dichaea）广泛分布于新热带区，包含逾100个物种，其长茎上着生二列叶、无假鳞茎，且花朵具柱头下舌片（infrastigmatic ligules），易于识别。此前该属主要依据子房是否具刚毛以及叶片是否具离层，被划分为4个组。本研究旨在利用DNA序列数据，解析Dichaea属内的系统发育关系，并绘制曾用于划分亚属/组的主要形态性状的分布格局。 研究方法：本研究选取67个内类群与7个外类群操作分类单元（operational taxonomic units, OTU），对其核核糖体内部转录间隔区以及质体matK、trnL内含子、trnL-F间隔区和ycf1序列进行扩增测序，以解析Dichaea属的系统发育关系。研究涵盖了此前划分的4个组的所有类群，其中以类群最丰富且分类学争议最大的Dichaea组样本量最大。 主要结果：分子数据与形态学证据均支持Dichaea属为单系群。结果显示Dichaeopsis组为多系群，其界定依据的是祖征（symplesiomorphies），包括在Zygopetalinae亚族中广泛分布的落叶叶与光滑子房。Dichaeopsis组内至少存在3个支持度较高的演化支。Pseudodichaea组为单系群，其界定特征为子房具刚毛且叶片具离层。Dichaea组与Dichaeastrum组均为单系群，二者以悬垂生长习性与宿存叶为界定特征。Dichaeastrum组主要以子房无毛与Dichaea组相区分，但该组可能为多系群。 研究结论：叶片离层仅发生一次演化丢失事件，仅存在于衍生的Dichaea组与Dichaeastrum组中。具刚毛的果实属于趋同演化性状（homoplasious character），在该属内多次出现得失演化。本研究基于5个支持度较高的演化支，提出该属的非正式分组方案。