Studies on the genetic structure and genetic subdivision of white spotted bamboo shark, Chiloscyllium plagiosum, by analysing mitochondrial Cyt b genes

The genetic diversity and genetic structure of Chiloscyllium plagiosum were assessed from three populations (Hainan, Guangdong, and Fujian), using mitochondrial Cyt b sequences. The complete mitochondrial Cyt b gene sequences (1146 nucleotides) from 71 individuals were defined as 15 haplotypes by 15 polymorphic sites after sequence alignment. The low levels of nucleotide diversity (π=0.00254) and haplotype diversity (h = 0.7195)indicated slow rate of mitochondrial DNA evolution in C. plagiosum . The result of selective neutrality tests (Tajima's D, P>0.10) suggested that there was no population expansion of the C. plagiosum in these three areas and the sizes of the three populations were relatively stable. The phyloge- netic tree and the network based on haplotype indicated that the population in Guangdong was the ancestor, while the group in Fujian appeared recently. The results of genetic distance and gene flow analysis and the results of AMOVA revealed distinct genetic differentiations between Hainan and Fujian groups and between Guangdong and Fujian groups, while the genetic dif- ferentiation is not significant between Hainan and Guangdong groups. Our research suggested that population differentiation occurred as a consequence of isolation-by-distance.