淡水豚类mtDNA 16S rRNA基因的系统发生

Phylogeny of the River Dolphins Based on Partial DNA Sequence from Mitochondrial 16S Ribosomal RNA Gene

mt DNA 16 S r RNA基因序列分析支持将现生淡水豚 4个属归入不同的科 ,即白暨豚科(L ipotiidae)、恒河豚科 (Platanistidae)、亚河豚科 (Iniidae)和弗西豚科 (Pontoporidae) .基于邻接法的系统发生分析显示淡水豚类由白暨豚 +恒河豚和弗西豚 +亚河豚两个单系组成 ,但两个单系之间并无姊妹关系 .淡水豚类是并系的 .16 S r RNA基因的系统发生树与 mt DNA细胞色素 b基因和12 S r RNA基因的系统发生树并不完全一致 .这种差异一方面可能反映了不同的基因树间的差异 ,但也可能与本文分析的 16 S r RNA基因片段中变异位点数和简约信息位点数较少有关 .因此 ,有必要增加序列长度来进一步验证 .

Supported by the sequence analysis of mitochondrial 16S ribosomal RNA (rRNA) gene, the four genera of the extant river dolphins should be referred to separate families, i.e. Lipotiidae、Platanistidae、Iniidae, and Pontoporidae. The phylogenetic analysis using neighbor joining method supported that the river dolphins consisted of two monophyletic clades, Lipotiidae + Platanistidae and Iniidae + Pontoporidae, but no sister relationship was revealed between the two clades. The river dolphins were paraphyletic. However, the relationship revealed by the 16S rRNA gene was different from those revealed by mitochondrial 12S rRNA and cytochrome b genes. The difference may be a reflection of the variation among different gene trees. On the other hand, the difference may also be related to the fewer variable sites and parsimony informative sites detected in the present gene sequences. Therefore, it is necessary to testify the river dolphin phylogeny using longer sequences.