18S rRNA基因在节肢动物系统进化研究中的意义

ARTHROPOD PHYLOGENY INFERRED FROM ENTIRE 18S rRNA SEQUENCES

采用多种分析方法对 4 0种节肢动物的 1 8Sr RNA基因全序列进行了分子系统学研究 ,结果表明 ,现生 4个类群的系统发生关系为 ( (多足类 +鳌肢类 ) (昆虫类 +甲壳类 ) ) ,且表现为辐射状 (爆发式 )分支形式 ;甲壳类的各个类群间也呈爆发式进化 ;介形类的速足介和丽足介两个类群是非单系起源的 ,它们的分化发生在甲壳纲各类群的分化之前 ;所有分析均显示速足介类支系中的金星介科的文杜维异壳介 ( H eterocypris vandouwei)、中华薄壳介 ( Dolerocyprissinensis)、Stenocyprismajor和 H eterocyprissp.组成一个单系类群。

Arthropod phylogenetic analyses using entire sequences of 18S rRNA gene of 40 species show that a rapid radiative evolutionary event may exist in the early evolution of arthropods. It is possible that same kind of pattern occurred in crustaceans immediately after the explosive evolution in arthropods. Podocopid and myodocopid ostracods are not monophyletic and the divergence of these two groups occurred before the explosive evolution of crustaceans. Neighbor joining and maximum likelihood analyses show that Cyprididae ( Heterocypris vandouwei,Dolerocypris sinensis,Stenocypris major and Heterocypris sp.) constitute a monophyletic group.