海菜花属的分支学研究

本文选取了与海菜花属系统发育有重要关系的19个性状,采用分支分析方法,研究了代表中国海菜花属全部已知分类群的18个居群的系统发育关系;根据简约性原则,构建了18个居群的分支图。结果表明,18个居群可划分为4类,它们分别对应于现知的4个分类学种,而与数值分类学研究中的Q分析结果基本一致;在分类群的划分上,分支分析与Q分析一样有效,并能反映系统发育关系。本文最后对海菜花属的起源和演化作了探索性推测,认为本属可能最迟在白垩纪末起源于冈瓦纳古陆的热带湖沼地区,此后分化成沉水叶多花支、沉水叶单花支和浮水叶单花支繁衍演化。

CLADISTIC STUDIES ON THE GENUS OTTELIA (HYDROCHARITACEAE)

Based on analysing the evolutionary polarities of 19 characters having important bearing on the phylogenetic relationships of the genus Ottelia, the present paper, by applying Wagner parsimony, dealt with the phylogenetic relationships among the 18 populations representing all the species of Ottelia so far known in China. A reasonable cladogram of the populations is constructed. The results suggest that the 18 populations could be classified into 4 groups corresponding to 4 taxonomic species. This is in conformity with the results of Q cluster analysis. The results indicate that cladistic analysis is not only as effective as Q cluster analysis in grouping taxa, but also could reveal the phylogenetic relationships of the taxa in question. Finally, the genus is postulated to originate in the areas of tropical lakies and swamps on Gondwanaland not later than Cretaceous period, and thereafter it evolves into three branches, i.e. polyovaries, submersed leaved-uniovary and floating leaved-uniovary branch, respectively.