title: Genetic structure of populations of whale sharks among ocean basins and evidence for their historic rise and recent decline.
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.
authors.affiliation: Laboratoire d'Excellence «CORAIL» USR 3278 CNRS - EPHE, CRIOBE, Papetoai, Moorea, French Polynesia.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Vignaud
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Maynard
authors.forename: Raphael
authors.initials: R
authors.lastname: Leblois
authors.forename: Mark G
authors.initials: MG
authors.lastname: Meekan
authors.forename: Ricardo
authors.initials: R
authors.lastname: Vázquez-Juárez
authors.forename: Dení
authors.initials: D
authors.lastname: Ramírez-Macías
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Pierce
authors.forename: David
authors.initials: D
authors.lastname: Rowat
authors.forename: Michael L
authors.initials: ML
authors.lastname: Berumen
authors.forename: Champak
authors.initials: C
authors.lastname: Beeravolu
authors.forename: Sandra
authors.initials: S
authors.lastname: Baksay
authors.forename: Serge
authors.initials: S
authors.lastname: Planes
mesh_terms: D000818:Animals; D001315:Australia; D004272:DNA, Mitochondrial / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D018895:Microsatellite Repeats; D009792:Oceans and Seas; D017422:Sequence Analysis, DNA; D012754:Sharks / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial
keywords: Rhincodon typus; demographic history; genetic diversity; microsatellites; molecular ecology mtDNA; population expansion