The Evolutionary History of a Coastal-Pelagic Species: The Global Phylogeography of the Tiger Shark (Galeocerdo cuvier)

The tiger shark is a globally distributed, highly mobile, dietary generalist predator that plays an important role in community structuring. The population dynamics of this fishery exploited apex predator remain enigmatic in most parts of its range. We investigated the global genetic population structure and phylogeography of tiger sharks utilizing a multi-locus approach [10 nuclear microsatellite loci (n = 389) and two mitochondrial loci: control region (mtCR) (1,068 bp; n = 349) and cytochrome oxidase I (642 bp; n = 152)]. With respect to population structure, western Atlantic and Indo- Pacific tiger sharks were found to be highly genetically differentiated using all three sets of genetic markers; however, intra-basin population structure appears to be much more complex. For instance, patterns of genetic isolation by distance were detected using mtCR in the western Atlantic, and microsatellite DNA in the Indo-Pacific. Investigation into the evolutionary history of the tiger shark using coalescent analyses of the mtCR suggest an Indo-Pacific center of origin for the tiger shark, followed by colonization into the western South Atlantic via South Africa during the Pleistocene. Interestingly, tiger sharks collected from the western South Atlantic possess a number of unique mtCR haplotypes, but also haplotypes occurring in both the western North Atlantic and the Indo-Pacific. Overall analyses (diversity- and coalescent-based) suggest that the western South Atlantic was likely an important historical connection that facilitated dispersal between basins, allowing the tiger shark to attain its contemporary global distribution.