基于12SrRNA序列研究龟鳖类的系统进化特征

为研究龟鳖类的系统进化关系,以期为龟鳖类的保护和合理开发利用提供基础资料,测定了15种龟类线粒体12SrRNA基因片段的序列。比对后获得一致序列长为433 bp,有191个变异位点,总变异率为43.2%,其中简约信息位点108个。A、T、G、C的平均含量分别为21.46%、34.42%、25.85%和18.27%。A+T含量(55.9%)高于G+C含量(44.2%)。在433个核苷酸位点中,有插入/缺失35个,转换为34,颠换为21,转换/颠换比率为1.67。与NCBI上其它一些龟鳖的序列进行比对后,得到414 bp的一致序列,其中236个为变异位点,总变异率为57.00%;简约信息位点181个。A、T、G、C的平均含量分别为35.7%、22.2%、18.1%、24.0%。A+T含量(57.9%)高于G+C含量(42.1%)。在414个核苷酸位点中,转换为30,颠换为14,转换/颠换比率为2.12。基于Kimura双参数模型分析龟鳖类种间、属间、科间遗传距离,并用邻接法构建分子系统树。结果显示:7种闭壳龟种间差异在0~0.043,平均为0.022;淡水龟科属间遗传距离为0.007~0.140,平均为0.074;曲颈龟亚目9个科间(不包括平胸龟)遗传距离为0.055~0.197,平均为0.139。由此认为,淡水龟科与陆龟科亲缘关系比龟科更近;不支持将闭壳龟属拆分为闭壳龟属和盒龟属;支持将平胸龟属归为鳄龟科的一个属。

Phylogenetic relationships of tortoises inferred from mtDNA 12SrRNA sequence

Mitochondrial 12SrRNA gene segment sequences of 15 tortoises individuals were obtained by using PCR amplification and sequencing.After alignment,433 bp consensus sequences of 12SrRNA were obtained.Among them,191 variable sites were detected,accounting for 43.2% of total sequences,and 108 were parsim-informative sites.The average content of A,T,G,and C were 21.46%,34.42%,25.85%,and 18.27%,respectively.The content of A+T(55.9%) is bigger than that of G+C(44.2%).Among the 433 nucleotide sites,34 transitional and 21 transversional sites with 35 indels were found,and the ratio between transition and transversion was 1.67.We downloaded the 12SrRNA sequences of other tortoise species from NCBI and analyzed the phylogenetic relationships between them together with our own sequences.After alignment,414 bp consensus sequences of 12SrRNA were obtained.236 variable sites were detected in all tortoises individuals,accounting for 57.00% of total sequences,with 181 parsim-informative sites.The average content of A,T,G,and C were 35.7%,22.2%,18.1%,and 24.0%,respectively.The content of A+T(57.9%) is bigger than that of G+C(42.1%).Among the 414 nucleotide sites,30 transitional and 14 transitional sites were found,and the ratio between transition and transversion was 2.12.Interspecific,intergenus,and interfamily genetic distances were calculated using the Kimura 2-parameter model with the pairwise deletion option.The NJ method was used to perform phylogenetic analysis.Results indicated that Bataguridae was closer to Testudinidae than that of Emydidae to Testudinidae.Results did not support the idea that the genus Cuora should be divided into two genera,Cuora and Cistoclemmys,but supporting the opinion that Platysternon should be refered to as a genus within Chelydridae.