Global population genetic dynamics of a highly migratory,apex predator shark |
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| Authors: | Andrea M. Bernard Kevin A. Feldheim Michael R. Heithaus Sabine P. Wintner Bradley M. Wetherbee Mahmood S. Shivji |
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| Affiliation: | 1. Save Our Seas Shark Research Center, Halmos College of Natural Sciences & Oceanography, Nova Southeastern University, Dania Beach, FL, USA;2. The Field Museum of Natural History, Pritzker Laboratory for Molecular Systematics and Evolution, Chicago, IL, USA;3. School of Environment and Society, Florida International University, Miami, FL, USA;4. KwaZulu‐Natal Sharks Board, Umhlanga Rocks, South Africa;5. Biomedical Resource Unit, University of KwaZulu‐Natal, Durban, South Africa;6. Department of Biological Sciences, University of Rhode Island, Kingston, RI, USA;7. Guy Harvey Research Institute, Dania Beach, FL 33004, USA;8. Save Our Seas Shark Research Center and Guy Harvey Research Institute, Halmos College of Natural Sciences & Oceanography, Nova Southeastern University, Dania Beach, FL, USA |
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| Abstract: | Knowledge of genetic connectivity dynamics in the world's large‐bodied, highly migratory, apex predator sharks across their global ranges is limited. One such species, the tiger shark (Galeocerdo cuvier), occurs worldwide in warm temperate and tropical waters, uses remarkably diverse habitats (nearshore to pelagic) and possesses a generalist diet that can structure marine ecosystems through top‐down processes. We investigated the phylogeography and the global population structure of this exploited, phylogenetically enigmatic shark by using 10 nuclear microsatellites (n = 380) and sequences from the mitochondrial control region (CR, n = 340) and cytochrome oxidase I gene (n = 100). All three marker classes showed the genetic differentiation between tiger sharks from the western Atlantic and Indo‐Pacific ocean basins (microsatellite FST > 0.129; CR ΦST > 0.497), the presence of North vs. southwestern Atlantic differentiation and the isolation of tiger sharks sampled from Hawaii from other surveyed locations. Furthermore, mitochondrial DNA revealed high levels of intraocean basin matrilineal population structure, suggesting female philopatry and sex‐biased gene flow. Coalescent‐ and genetic distance‐based estimates of divergence from CR sequences were largely congruent (dcorr = 0.0015–0.0050), indicating a separation of Indo‐Pacific and western Atlantic tiger sharks <1 million years ago. Mitochondrial haplotype relationships suggested that the western South Atlantic Ocean was likely a historical connection for interocean basin linkages via the dispersal around South Africa. Together, the results reveal unexpectedly high levels of population structure in a highly migratory, behaviourally generalist, cosmopolitan ocean predator, calling for management and conservation on smaller‐than‐anticipated spatial scales. |
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| Keywords: | genetic population structure microsatellite DNA mitochondrial DNA phylogeography tiger shark |
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