Variability Of The Mitochoadrial DNA Control Region Of Bottlenose Dolphins(genus:Tursiops)and Application Of C-mos Gene In The Study Of Cetacean Phylogeny

This thesis includes four chapters:1. The progress of the study on molecular phylogeny of cetaceans was reviewed.2. The method to extract genome DNA from old skeletal specimens of cetaceans was improved and the PCR amplification reaction was optimized. By purifying the extracted template DNA and using touchdown PCR and nested PCR techniques, the targeted c-mos gene segment was amplified successfully to clone and sequence.3. Four hundred and twenty-four base pairs (bp) of the mitochondria! control region from 30 bottlenose dolphins (Tursiops spp.) collected from the Yellow and East China Seas, the Taiwan Strait, and the Gulf of Beibuwan were sequenced. Combined with previously published mtDNA control region sequences of other bottlenose dolphins from Chinese waters, 54 variable sites were determined and 37 haplotypes were identified. No shared haplotypes were found between truncatus- and aduncus-type of bottlenose dolphins, and eight fixed diagnostic site differences separated the two morphotypes. Phylogenetic relationships reconstructed by using the maximum likelihood method and neighbor joining methods divided the 37 haplotypes into two monophyletic clades representing the two morphotypes. The average nucleotide divergence between the two morphotypes is 5.58%, which was about five times greater than between Delphimts species (1.09%). These supported the conclusion that the two morphotypes of bottlenose dolphins hi Chinese waters represented distinctspecies, i.e. T. tnmcatus and T. aduncus. Net nucleotide divergence between the two species was 3.79%. Although the distribution of the two species overlapped in the Taiwan Strait (and maybe adjacent waters), there is no genetic interchange between them, indicating reproductive isolation between the two species.4. The primers for amplifying the cetacean c-mos genes were designed based on the conservative region of c-mos genes from pigs and some other mammals. With these primers, the cetaceans c-mos partial encoding region (546bp) was amplified and sequenced from 24 individuals of toothed whale including 12 species of 5 families. The result suggested that level of sequence variation of cetacean c-mos genes was low. hi the phylogenetic analysis, the species belonging to the same family constituted respective monophyletic group, but the relationship at subfamily level was not well resolved. This suggested that c-mos gene is a fit candidate gene in the phylogenetic analysis at family and higher level, but not appropriate at taxa lower than family.