Abstract
Carcharhinus limbatus has a cosmopolitan distribution and marked genetic structuring, mainly because of its philopatric behavior. However, analysis of this structuring has not previously included South American populations. In the present study, we analyzed a sample of adult individuals collected on the northern coast of Brazil and compared the sequences of the mitochondrial control region with those of populations already genotyped. Relatively high haplotype diversity (12 haplotypes, genetic diversity of 0.796) was observed, similar to that in other populations but with a much larger number of private alleles. In contrast to populations studied previously, which were represented by neonates, the pronounced allelic variability found in the South American individuals may have resulted from migrations from other populations in the region that have yet to be genotyped. This population was also genetically distinct from the other Atlantic populations (Fst > 0.8), probably because of female philopatry, and apparently separated from the northwestern Atlantic group 1.39 million years ago. These findings indicate that the C. limbatus population from northern Brazil is genetically distinct from all other populations and should be considered as a different management unit for the protection of stocks.
Highlights
Sharks are vulnerable to overexploitation by fisheries because of their low fecundity and slow maturation (Musick et al, 2000; Myers and Worm, 2005; Tsai et al, 2010; Tillett et al, 2011) and their limited potential for recruitment
Identification of the genetic structuring of populations is fundamental for determining whether and to what degree reproductive isolation exists, and can identify subpopulations that need to be treated as separate management units (Palsboll et al, 2007)
Sequences of the control region 1067-1070 base pairs in length were obtained for 25 specimens of C. limbatus
Summary
Sharks are vulnerable to overexploitation by fisheries because of their low fecundity and slow maturation (Musick et al, 2000; Myers and Worm, 2005; Tsai et al, 2010; Tillett et al, 2011) and their limited potential for recruitment This combination of traits has resulted in a sharp decline in populations in many parts of the world (Baum and Myers, 2004; Bradshaw et al, 2008; Ferretti et al, 2010). Traits such as the lack of mobile larvae or philopatric behavior may limit gene flow and result in the genetic divergence of populations of marine organisms, even when they have a continuous distribution (Meylan et al, 1990)
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