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. 2017 May 24;7(13):4768-4781.
doi: 10.1002/ece3.2987. eCollection 2017 Jul.

World without borders-genetic population structure of a highly migratory marine predator, the blue shark (Prionace glauca)

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World without borders-genetic population structure of a highly migratory marine predator, the blue shark (Prionace glauca)

Ana Veríssimo et al. Ecol Evol. .

Abstract

Highly migratory, cosmopolitan oceanic sharks often exhibit complex movement patterns influenced by ontogeny, reproduction, and feeding. These elusive species are particularly challenging to population genetic studies, as representative samples suitable for inferring genetic structure are difficult to obtain. Our study provides insights into the genetic population structure one of the most abundant and wide-ranging oceanic shark species, the blue shark Prionace glauca, by sampling the least mobile component of the populations, i.e., young-of-year and small juveniles (<2 year; N = 348 individuals), at three reported nursery areas, namely, western Iberia, Azores, and South Africa. Samples were collected in two different time periods (2002-2008 and 2012-2015) and were screened at 12 nuclear microsatellites and at a 899-bp fragment of the mitochondrial control region. Our results show temporally stable genetic homogeneity among the three Atlantic nurseries at both nuclear and mitochondrial markers, suggesting basin-wide panmixia. In addition, comparison of mtDNA CR sequences from Atlantic and Indo-Pacific locations also indicated genetic homogeneity and unrestricted female-mediated gene flow between ocean basins. These results are discussed in light of the species' life history and ecology, but suggest that blue shark populations may be connected by gene flow at the global scale. The implications of the present findings to the management of this important fisheries resource are also discussed.

Keywords: gene flow; highly migratory sharks; nursery areas; panmixia.

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Figures

Figure 1
Figure 1
Sampling locations of blue sharks in Atlantic waters. Triangles—Iberian Peninsula, squares—Azores, circles—western South Africa, diamond—western Brazil. Black symbols—individuals from cohorts between 2003 and 2008 (2000s), white symbols—in dividuals from cohorts between 2012 and 2015 (2010s)
Figure 2
Figure 2
Mitochondrial control region haplotype network and Bayesian inference (BI) tree based on Atlantic blue shark sample collections. Number of mutated positions among connected haplotypes in the network are indicated by the slash marks. Numbers on the tree branches are BI probabilities. Black circles indicate inferred (i.e., not observed) haplotypes
Figure 3
Figure 3
Discriminant analysis of principal components of (a) 11 microsatellite loci genotyped at the three Atlantic nursery sample collections, and (b) six microsatellite loci genotyped at the three nursery areas and the Brazil sample collections

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