瑞香属和荛花属的数量分类研究

瑞香属和荛花属为瑞香科瑞香亚科的落叶或常绿灌木,中国西南部是瑞香属和荛花属的重要分化中心。全世界共有瑞香属95种、荛花属70种,中国分布有瑞香属52种、荛花属49种。瑞香属和荛花属的分类学研究一直存在不同程度的分歧。花盘形状和果实类型在传统分类中一直是区分瑞香属和荛花属的典型特征,而花盘形态和果实类型在2个属中存在交叉和过渡,部分植物分类学家根据这些特征将两个属进行过不同程度的归并。该研究采用数量分类法对瑞香属77种(变种)和荛花属62种(变种)植物,选取32个形态学性状进行聚类分析和主成分分析。结果表明:聚类分析和主成分分析均显示两属均未形成单系类群。在主成分分析中,前3个主成分分析的贡献值为35.56%,传统分类中用来区分两属的花盘形状、叶序及果实类型等特征对前3个主成分贡献相对较小,因此,传统分类学中对这两个属进行区分的性状并没有典型的分类学意义。同时,聚类图和主成分分析得到的散点图均不能将这两个属区分开来。数量分类研究结果显示两属植物存在明显的交叉,支持瑞香属和荛花属不是两个独立自然类群的观点。

Numerical taxonomy of the genera Daphne and Wikstroemia

Daphne and Wikstroemia are members of subfamily Thymelaeoideae which belongs to Thymelaeaceae. There are 95 species(varieties)in genus Daphne, 52 of which distribute in China. There are 70 species(varieties)in genus Wikstroemia and 49 species(varieties)can be found in China. Southwest China is the species diversification center of the two genera. Petals of Daphne and Wikstroemia degenerate and usually form circular disc or linear disc scale. Conventionally, the shape of disc and type of fruit were used as crucial characters to separate the two genera. The circular disc frequently occurs in Daphne while linear disc scale occurs in Wikstroemia. Meanwhile, fruit is usually succulent berry in Daphne, but Wikstoemia has dry or leathery fruit, and sometimes enclosed by persistent calyx. However, alternational characters among species of the two genera have been reported and some species have both kinds of characters. In this study, 32 morphological characters were used in the numerical taxonomy of 77 species(varieties)from genus Daphne and 62 species(varieties)from genus Wikstroemia with clustering and principal component analysis. UPGMA clustering results revealed that neither genera formed monophyletic group species from the two genera clustered together. In the principal components analysis, the cumulative percent of the first three principal components presented 35.56%, while the conventional taxonomic characters, such as the disc shape, phyllotaxy and the fruit type, contribute minor effects on the first three components. So, taxonomic distinguishable characters of the two genera could not separate them clearly. Three-dimensional scatter plots based on principal components analysis revealed that species from both genera embeded with each other and did not separate two genera as monophyletc group. Neither clustering analysis nor principal components analysis supported the traditional taxonomy that Daphne and Wikstroemia were naturally monophyletic groups.