Abstract
Human activities have resulted in the loss of over 90% of sharks in most ocean basins and one in four species of elasmobranch are now listed at risk of extinction by the IUCN. How this collapse will affect the ability of populations to recover in the face of continued exploitation and global climate change remains unknown. Indeed, important ecological and biological information are lacking for most shark species, particularly estimates of genetic diversity and population structure over a range of spatial scales. Using 15 microsatellite markers, we investigated genetic diversity and population structure in gray reef sharks over their Indo-Pacific range (407 specimens from 9 localities). Clear genetic differentiation was observed between the Indian and the Pacific Ocean specimens (FST = 0.145***). Further differentiation within the Pacific included a West and East cleavage as well as North-Central and South-Central Pacific clusters. No genetic differentiation was detected within archipelagos. These results highlight the legacy of past climate changes and the effects of large ocean expanses and circulation patterns on contrasting levels of connectivity at global, regional and local scales. Our results indicate a need for regional conservation units for gray reef sharks and pinpoint the isolation and vulnerability of their French Polynesian population.
Highlights
Human activities have resulted in the loss of over 90% of sharks in most ocean basins and one in four species of elasmobranch are listed at risk of extinction by the IUCN
Reef shark studies have demonstrated significant genetic structure and variable demographic histories for blacktip reef sharks over their Indo-Pacific range[14], and female blacktip reef sharks were shown to be philopatric in French Polynesia[15]
Private allele numbers per sampling site ranged from 0 to 18 while there was a total of 143 alleles found exclusively in the Pacific Ocean and 10 alleles recovered only from the western Indian Ocean
Summary
Human activities have resulted in the loss of over 90% of sharks in most ocean basins and one in four species of elasmobranch are listed at risk of extinction by the IUCN How this collapse will affect the ability of populations to recover in the face of continued exploitation and global climate change remains unknown. Using 15 microsatellite markers, we investigated genetic diversity and population structure in gray reef sharks over their Indo-Pacific range (407 specimens from 9 localities). No genetic differentiation was detected within archipelagos These results highlight the legacy of past climate changes and the effects of large ocean expanses and circulation patterns on contrasting levels of connectivity at global, regional and local scales. While reef characteristics such as geography and oceanographic context likely play an important role, more specific factors regulating dispersal of gray reef sharks remain unknown
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