亚洲淡水和陆生龟鳖类12S rRNA基因片段的序列分析和系统发生研究

PHYLOGENY OF ASIAN FRESHWATER AND TERRESTRIAL TURTLES BASED ON SEQUENCE ANALYSIS OF 12S rRNA GENE FRAGMENT

对亚洲产淡水和陆生龟鳖类4科23个种进行了DNA序列水平的分子系统学研究，用PCR技术扩增约400bp的线粒体12SrRNA基因片段并进行了序列分析，合并从GenBank中检索到的其它龟鳖类的序列数据，在基于二级结构的对位排列基础上用邻结法进行了系统发生研究。结果表明，潮龟科与陆龟科的亲缘关系比龟科与陆龟科的近；支持将平胸龟属归为鳄龟科的1个属；潮龟科是并系起源的，从12SrRNA基因序列得到的系统发生关系不支持根据形态学和染色体性状对潮龟科的分亚科和分组。根据12SrRNA基因片段的序列差异和化石记录的分歧时间计算得到的颠换积累速率，支持龟鳖类mtDNA慢速率进化理论。

Molecular systematic analysis of 23 species of Asian freshwater and terrestrial turtles was performed at level of DNA sequence in this study. A 400bp fragment of mitochondrial 12S rRNA gene from each species was amplified with PCR technique and the PCR products were sequenced. Together with sequence data of other turtles retrieved from GenBank, the phylogenetic analysis was carried out from alignmented sequence based on the secondary structure using NJ method. The resu1ts indicate that Bataguridae has a closer relationship with Testudinidae than that of Emydidae with Testudinidae, supporting the opinion that Platysternon should be referred as a genus of Chelydridae. Although Bataguridae is paraphyletic, the opinion of its dividing of subfamilies and complexes according to morphological and chromosomal characters is not supported by the phylogenetic relationship obtained from the sequence of 12S rRNA gene. Transversion accumulating rate of 12S rRNA is estimated as 0. 023% per million years according to sequence difference and divergence time estimated by fossil records. This rate is lower than O. 1 %～0. 2% in mammals and therefore, supports the hypothesis of low rate evolution of mtDNA in turtles.