中国绿水螅分子系统发生地位的初步探讨

目的:初步探讨中国绿水螅(Hydra sinensis)分子系统发生地位以及水螅属内部各类群系统发生关系。方法:采用酚-氯仿法提取中国绿水螅总DNA,扩增线粒体COI和16S r RNA基因片段并进行DNA序列测定,再利用Clustal及MEGA等生物信息学分析软件进行系统发生分析。结果:在本研究重建的所有系统发生树中,中国绿水螅始终与绿水螅Hydra viridissima的不同种群一起构成绿水螅单系群。同时,棕色水螅群的单系性被基于COI基因的NJ树以及基于16S r RNA基因的NJ树和ML树支持,唯独基于COI基因的ML树不支持棕色水螅群的单系发生。在基于COI基因的ML树中纤弱水螅族在系统树的基部独立为一支系,而绿水螅群和其他棕色水螅群水螅一起组成另一支系,提示纤弱水螅族水螅的系统发生地位值得进一步探讨。值得注意的是,根据本文的结果,棕色水螅群内3族的划分仍然有一定疑问。基于COI基因的NJ树和ML树支持普通水螅族、寡水螅族和纤弱水螅族各自族内的单系发生,但16S r RNA基因的NJ树和ML树中仅普通水螅族水螅聚为单系群,而寡水螅族和纤弱水螅族水螅各自并非单系发生。结论:把水螅属划分为绿水螅群及棕色水螅群有一定的合理性,但棕色水螅群内寡水螅族、普通水螅族和纤弱水螅族3族的划分还有待商榷。

Primary Study on Molecular Phylogenetic Position of Chinese Green Hydra

Objective:To investigate the molecular phylogenetic position of Chinese green hydra (Hydra sinensis ) as well as the phylogenetic relationships among different groups of the Genus Hydra.Methods:After the total genomic DNA of Chinese green hydra was extracted following standard proteinase digestion and phenol-chloroform extraction procedures, the mitochondrial COI and 16S rRNA gene DNA fragments were amplified and sequenced. Bioinformatics analysis software such as Clustal and MEGA were used for phylogenetic analysis of the Hydra sinensis.Results:In all the reconstructed phylogenetic tree, the Chinese green green hydra and the different populations of green hydra Hydra sinensis always formed a monophyletic group. Meanwhile, the NJ tree based on COI gene, the NJ and ML tree based on 16S rRNA gene supported the monophyly of brown hydras that were not monophyletic in the ML tree based on COI gene. In the ML tree based on COI gene, braueri group was an independent clade at the base of the tree, while green group and other brown hydra groups formed another branch. In addition, according to the results of this paper, whether brown hydras should be divided into three groups (vulgaris group, oligactis group, braueri group) is still a problem to solve. Vulgaris group, oligactis group and braueri group were monophyletic respectively in the NJ and ML tree based on COI gene, while vulgaris group was monophyletic in the NJ and ML tree based on 16S rRNA gene, while oligactis group and braueri group were polyphyletic respectively.Conclusion:It has a certain rationality that the Hydra sinensis is divided into green and brown hydras, but whether brown hydras should be divided into three groups remains a problemto solve.