Cosmopolitan pelagic species often show shallow genetic divergence and weak, or no, genetic structure across a species’ range. However, there have been few such genetic studies for pelagic sharks. The pelagic blue shark (Prionace glauca) has a broad circumglobal distribution in tropical and temperate oceans. To investigate the population genetic structure and demographic history of this species, we analysed variation in the mitochondrial cytochrome b sequence for a total of 404 specimens collected from 10 locations across the Indo-Pacific region. The observed genetic diversities were comparable among sampling locations (h=0.77–0.87; π=0.17–0.23%). Spatial analysis of molecular variance (SAMOVA), pairwise ΦST and conventional FST estimates, and analysis of isolation with migration indicated weak or no genetic differentiation of this species across the Indo-Pacific region. The results of three phylogeographic analyses (i.e. mismatch distribution and parsimony haplotype network analyses and a neutrality test) suggested that the Pacific blue shark had historically experienced a sudden population expansion. These results, coupled with the biological properties of this species, imply that historical climate fluctuation has had only a minor effect on the genetic structuring of the blue shark.
Population genetic structure, phylogeography and demographic history of Hilsa shad (Tenualosa ilisha) in the Indian Ocean region
