江豚线粒体Cyt b和D-loop片段序列分析及其分子系统学研究

Sequence analysis of mitochondral Cyt b gene,D-loop and molecular phylogeny of Neophocaena phocaenoides

对江豚(Neophocaena phocaenoides)mtDNA的Cytb(377bp)和D-loop(343bp)片段进行了测序和分析,并与GenBank中鼠豚类及一角鲸类同源序列进行了比较。研究结果表明,Cytb基因片段的碱基组成平均为T:29.0%,C:28.8%,A:27.2%,G:15.0%;D-loop片段的碱基组成平均为T:35.9%,C:21.8%,A:32.4%,G:9.9%。Cytb基因片段共出现109个变异位点,简约信息位点107个,序列变异度为28.9%,碱基替代主要发生在密码子第3位点上,转换/颠换为13.3;D-loop片段共有109个变异位点,简约信息位点100个,序列变异度为31.8%,转换/颠换为2.4。构建的系统发育树显示,江豚是鼠豚科中较早分化出来的一个类群,与一角鲸科的亲缘关系最近。2个片段序列的分析结果一致,棘鳍鼠海豚Phocoena spinipinnis、太平洋鼠海豚P.sinus和黑眶鼠海豚Australophocaena dioptria聚为一支。

The nucleotide composition and phylogenetic relationship among the species of Phocoenidae and Monodontieae were studied based on the 377 bp sequences of Cyt b gene and the 330 bp sequences of control region （D-loop）. For the Cyt b gene, the average nucleotide contents of T, C, A, and G were 29.0% , 28.8% , 27.2% and 15.0%, respectively; it had 109 variable sites, among which 107 were parsimony-informative, with a sequence variability of 28.9% ; two singletons and nucleotide substitution mostly occurred at the third position and the transformation was 13.3. For D-loop fragment, the average nucleotide T, C, A and G contents were 35.9% , 21.8%, 32.4% and 9.9% , respectively; 109 variable sites were detected in the eight species, among which 100 were parsimony-informative; the sequence variability was 31.8% and the transformation was 2.4. The phylogenetic trees showed that Neophocaena phocaenoides represented the most basal member of the family, having a most intimate affinity to Monodontieae. The results aslo indicated that the relationships among the taxa Phocoena sinus, P. spinipinnis and Australophocaena dioptrica were intimate.