Population Genetic Structure of Pantropical Spotted Dolphin, Stenella attenuata, in Waters of Taiwan and South China Sea Based on Mitochondrial DNA Control Region Sequences

A total of 447 base pairs of the mitochondrial DNA control region from 34 pantropical spotted dolphins, Stenella attenuata, in the waters of Taiwan and South China Sea were sequenced and analyzed. In this study, we tested the null hypothesis of non-differentiation genetic structure of the spotted dolphin of Taiwanese and adjacent waters. There were three putative populations in this study －Taiwan Strait, eastern Taiwan and South China Sea. The genetic structure and population differentiation of the putative populations were estimated to clarify the population status. There were 14 variable sites within the sequences and 13 haplotypes defined. Among the haplotypes, nine were unique and four were shared. The South China Sea population had three haplotypes, all of these were unique. The haplotype diversity estimates of the three populations range from 0.8883 in South China Sea, followed by 0.8182 in Taiwan Strait and 0.7778 in eastern Taiwan. Nucleotide diversity estimates range from 0.0096 in eastern Taiwan, 0.0078 in South China Sea and 0.0049 in Taiwan Strait. The Minimum-spanning network does not describe a clear pattern of haplotype and geographical locale relationship. Neighbor-joining and Maximum Likelihood phylogenetic analyses with Stenella longiroatris as outgroup also could not divide the haplotypes into clades representing the three putative populations. The Analysis of Molecular Variance (AMOVA) results show two patterns of population differentiation. The analysis using haplotype frequency, Fst, indicates significant population subdivision between South China Sea and Taiwan Strait (Fst = 0.1761, p = 0.0156), and between South China Sea and eastern Taiwan populations (Fst = 0.2029, p = 0.0059). However, the analysis using genetic distance and frequency information, Φst, does not reveal significant population differentiation between any pair of comparisons. Additionally, the relatively lower genetic diversity estimates of pantropical spotted dolphins in Taiwanese waters suggest that future monitoring is needed. A more systematic collecting method and expanding sampling area should be carried out for future investigations