Phylogenetic and morphometric relationships between two species of genus Auxis from the South China Sea and Java Sea

This study was aimed at examining the phylogenetic and morphometric relationship of frigate tuna(Auxis thazard) and bullet tuna(Auxis rochei) using mt DNA D-loop(control) region sequences and truss measurements,respectively. Maximum-likelihood(ML) tree and median-joining network showed that haplotypes from Auxis populations grouped separately. Discriminant function analyses and non-metric multidimensional scaling of morphometric data showed that bullet and frigate tuna were differed mainly with respect to truss measurements on the anterior region, suggesting adaptation to different diets available in different environments. Historic demographic analyses of sequence data showed that both bullet and frigate tuna had not undergone a significant sudden population expansion recently. Non-significant value of Tajimas’ s D and Fu’s Fwere indicated an effective large and stable population size for longer period of both species in South China Sea and Java Sea species. This study gives first report on the complementary relationship between morphometric and genetic analysis in stock discrimination of genus Auxis.