基于nrDNAITS序列数据的兰属系统发育关系的初步分析(英)

现存的兰属分类系统是基于宏观形态学性状、尤其是花粉块的数目以及唇瓣与蕊柱的愈合程度而建立的。兰属因此而划分为 3个亚属 :兰亚属 (subgenusCymbidium) ,大花亚属 (subgenusCyperorchis)和建兰亚属 (subgenusJensoa)。本文运用PCR扩增和直接测序的方法分析兰属 (Cymbidium) 2 7种、3个栽培品种以及 3个外类群的核DNAITS区段序列。通过最简约性分析产生的ITS系统发育树表明 ,兰属的 3个亚属均可能为不自然的类群。大花亚属表现为一复系群 ,兰亚属的冬凤兰 (C .dayanum )隐藏于其中 ;建兰亚属为一并系群 ,它的成员之一兔耳兰(C .lancifolium)偏离出去而成为兰属一最基部的分支 ;兰亚属为一复系群 ,它分为几支而分别与另两个亚属组合在一起。由于兰属ITS序列位点变异率较低 ,最简约性分析产生的几支主要分支均得不到Bootstrap分析的高度支持 ,各亚属内组之间的关系也不明确。研究兰属的系统发育关系还需要新的数据。

A Preliminary Analysis of Phylogenetic Relationships in Cymbidium (Orchidaceae) Based on nrITS Sequence Data

The infrageneric classification currently in use for Cymbidium is based on gross morphology, with emphasis on the number of pollinia and state of fusion between lip and column. The sequences of nrDNA regions of 27 species and 3 cultivars of Cymbidium and 3 outgroup species ( Eulophia graminea, Geodorum densiflorum, Amitostigma pinguiculum) were analyzed using PCR amplification and direct DNA sequencing. The phylogenetic trees generated from maximum parsimony analysis, however, show that the existing division among three subgenera (subgen. Cymbidium , subgen. Cyperorchis and subgen. Jensoa ) should be evaluated with more data. Subgenus Cyperorchis was not a monophyletic group, with the unexpected nesting of C. dayanum (subgen. Cymbidium ) within it; subgenus Jensoa also appeared paraphyletic, with C. lancifolium being the sister group to the remainder of the genus; species of subgen. Cymbidium appeared polyphyletic, being split into several clades and intermixed with the main subgen. Cyperorchis and subgen. Jensoa clades, respectively. However, because of the insufficiency of informative characters of ITS sequences, some of the clades identified, especially the major lineages of Cymbidium , received relatively low support; sectional delimitations were also not clear within each subgenus. Further study is needed for achieving a robust phylogeny of Cymbidium .