Abstract
The tiger shark (Galeocerdo cuvier) is a common widespread coastal-pelagic shark species whose population genetic structure has only recently been the object of genetic studies. In this study, the tiger's shark mitochondrial DNA control region was sequenced for a sample of 172 individuals from the western Atlantic and from Australia's east coast in the Pacific Ocean. The results show a moderate variation in genetic diversity (h = 0.615 +/- 0.038, pi = 0.00184 +/- 0.00021) with a strong population structure between Atlantic areas (phi(ST) = 0.28141, P = 0.00001). The maternal lineage has high site fidelity, which paradoxically is coupled with connectivity across open ocean stretches to Fernando de Noronha Archipelago, which is identified as an important hotspot for this species. These results help with the understanding of what drives the displacement of this shark, at intra- and/or inter-ocean basins levels, and can help inform the implementation of future conservation and management measures. We recommend that the conservation of genetic diversity should be maintained at a global level and its maintenance should be pursued diligently in all populations of tiger shark. As the Fernando de Noronha region in the western Atlantic appears to contain the largest global genetic diversity of the species, this area should be treated as a marine reserve or ecological refuge for the tiger shark.