Genetic structure of populations of whale sharks among ocean basins and evidence for their historic rise and recent decline |
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Authors: | Thomas M Vignaud Jeffrey A Maynard Raphael Leblois Mark G Meekan Ricardo Vázquez‐Juárez Dení Ramírez‐Macías Simon J Pierce David Rowat Michael L Berumen Champak Beeravolu Sandra Baksay Serge Planes |
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Institution: | 1. Laboratoire d'Excellence ?CORAIL? USR 3278 CNRS – EPHE, CRIOBE, , Papetoai, Moorea, French Polynesia;2. Department of Ecology and Evolutionary Biology, Cornell University, , Ithaca, NY, 14568 USA;3. INRA, UMR1062 CBGP, , F‐34988 Montferrier‐sur‐Lez, France;4. Australian Institute of Marine Science, UWA Oceans Institute (MO96), , Crawley, WA, 6009 Australia;5. Centro de Investigaciones Biologicas del Noroeste, , La Paz, B.C.S. 23096 Mexico;6. Tiburón Ballena México proyecto de Conciencia Mexico, , La Paz, B.C.S. 23090 Mexico;7. Marine Megafauna Foundation, , Oakley, CA, 94561 USA;8. Wild Me, Praia do Tofo, , Inhambane, Mozambique;9. Marine Conservation Society Seychelles, , PO Box 1299 Victoria, Mahe, Seychelles;10. Red Sea Research Center, King Abdullah University of Science and Technology, , 23955‐6900 Thuwal, Kingdom of Saudi Arabia |
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Abstract: | This study presents genetic evidence that whale sharks, Rhincodon typus, are comprised of at least two populations that rarely mix and is the first to document a population expansion. Relatively high genetic structure is found when comparing sharks from the Gulf of Mexico with sharks from the Indo‐Pacific. If mixing occurs between the Indian and Atlantic Oceans, it is not sufficient to counter genetic drift. This suggests whale sharks are not all part of a single global metapopulation. The significant population expansion we found was indicated by both microsatellite and mitochondrial DNA. The expansion may have happened during the Holocene, when tropical species could expand their range due to sea‐level rise, eliminating dispersal barriers and increasing plankton productivity. However, the historic trend of population increase may have reversed recently. Declines in genetic diversity are found for 6 consecutive years at Ningaloo Reef in Australia. The declines in genetic diversity being seen now in Australia may be due to commercial‐scale harvesting of whale sharks and collision with boats in past decades in other countries in the Indo‐Pacific. The study findings have implications for models of population connectivity for whale sharks and advocate for continued focus on effective protection of the world's largest fish at multiple spatial scales. |
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Keywords: | demographic history genetic diversity microsatellites molecular ecology mtDNA population expansion
Rhincodon typus
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