淡水豚类线粒体DNA12S rRNA基因的序列变异及其分子系统学研究

SEQUENCE VARIATION OF MITOCHONDRIAL 12S rRNA GENE AND INFERRED MOLECULAR SYSTEMATICS OF RIVER DOLPHINS

淡水豚类 4个代表属 [白暨豚 (Lipotes)、恒河豚 (Platanista)、弗西豚 (Pontoporia)和亚河豚(Inia) ]mtDNA 12SrRNA基因的序列差异水平 ,高于其他齿鲸类科间的差异 ,特别是远远高于海豚总科内的科间差异。研究结果支持它们应归属于不同的科 ,即白暨豚科 (Lipotiidae)、恒河豚科 (Platanistidae)、弗西豚科 (Pontoporidae)和亚河豚科 (Iniidae)。恒河豚科是鲸类中最早分化出来的独立支系 ,而其余 3个淡水豚科组成一个单系 ,作为海豚总科的姊妹群。淡水豚类的发生是多系的。白暨豚科、亚河豚科和弗西豚科是否隶属于同一个总科尚需进一步研究。

Partial DNA sequences of mitochondrial 12 S ?rRNA gene from Lipotes vexillifer,Platanista gangetica ,and Pontoporia blainvillei ,were amplified and determined to address the systematics of river dolphins. The sequence divergence among different genera of river dolphins,estimated either by transition+transversion or transversion only,is greater than those among other odontocete families,far greater than those among families Delphinidae,Monodontidae,and Phocoenidae within superfamily Delphinoidea. Thus,the river dolphin genera should be referred into different families,i e. Lipotidae,Platanistidae,Iniidae,and Pontoporiidae. The phylogenetic analysis by using neighbor joining method (NJ) and maximum parsimony method (MP) suggested that the Platanistidae was the earliest divergent clade in the cetaceans,whereas the other three river dolphin families constituted a monophyletic group having sister relationship with Delphinoidea. The phylogeny of river dolphins should be polyphyletic,rather than monophyletic or paraphyletic. The Platanistidae should be referred into a separated superfamily Platanistoidea,whereas the superfamily classification of other three river dolphin families should be further studied.