基于ITS2序列和形态学特征对泰山杜鹃属植物系统发育关系的分析

Phylogenetic relationship analysis of genus Rhododendron(Ericaceae) from Mountain Tai based on ITS2 sequences and morphological traits

为明确泰山现有照山白、迎红杜鹃、满山红、杜鹃、羊踯躅的系统分类,同时探讨杜鹃属(Rhododendron)内各亚属的系统发育关系,本研究以泰山现有杜鹃属的4个亚属5个种8个样本为研究对象,借助Gen Bank数据库,以扫帚岩须和吊钟花为外类群,分析了杜鹃属9个亚属92个种的内转录间隔区(ITS2)序列并构建分子系统发育树;同时选取其中18个代表种24个形态性状进行分析及表型性状分支分析树构建。结果表明:杜鹃属是一个多系类群,各亚属进化程度基本平衡。在泰山现有杜鹃属5个种中,照山白、迎红杜鹃、杜鹃、羊踯躅均聚在以各自亚属种为主的大支中,满山红未能聚在映山红亚属分支中。基于形态学特征的数量聚类结果显示,距离系数为18的水平线可作为亚属的划分界线。在分子聚类中,马银花亚属的长蕊组和马银花组与常绿杜鹃亚属的常绿杜鹃组分别得到较高的支持度,但常绿杜鹃组下的亚组间区分不明显,羊踯躅亚属和叶状苞亚属均位于系统发育树基部,符合形态学分类结果。

A study to evaluate the relationships in subgenus of Rhododendron and clarify classification of the native R. micranthum, R. mucronulatum, R. mariesii, R. simsii and R. molle in Mountain Tai was undertaken using both morphological traits and molecular analysis of the DNA sequence variation of the nuclear ribosomal internal transcribed spacer（ITS） regions. Phylogenetic tree was constructed, using maximum parsimony method, based on ITS2 sequences of 92 species, 9 subgenera, which included 8 samples of 5 species from Mountain Tai, 84 samples from Gen Bank database, Cassiope fastigiata and Enkianthus quinqueflorus as outgroups; phylogenetic analysis was performed on the basis of 24 phenotypic characters of 18 species representing 9 subgenuses. The results revealed that Rhododendron is a polyphyletic group, and evolutionary degree of each subgenus is balanced. Among the 5 species from Mountain Tai, the R. mariesii failed to gather in the branch of subg. Tsutsusi, and other 4 species were located in the major branches of their own subgenuses. The quantitative cluster analysis based on morphological features showed that the line of distance coefficient of 18 can be used as the demarcation line of the subgenus. The monophyly of sect. Choniastrum（subg. Azaleastrum）, sect. Azaleastrum（subg. Azaleastrum） and sect. Ponticum（subg. Hymenanthes） was strongly supported, while there was no significant difference between subsections in sect. Ponticum. Subgs. Pentanthera and Therorhodion were located at the base of phylogenetic tree, which was consistent with morphological classification results.