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Front. Mar. Sci. | doi: 10.3389/fmars.2019.00718

DNA analysis of juvenile scalloped hammerhead sharks Sphyrna lewini (Griffith & Smith 1834) reveals multiple breeding populations and signs of adaptive divergence in the South Pacific

  • 1University of the South Pacific, Fiji
  • 2INRA, UMR Ecologie et santé des écosystèmes ESE, France
  • 3Institute of Marine Sciences of Andalusia (ICMAN), Spain

Shark species have undergone drastic population declines in recent decades due to overfishing and habitat destruction; thus, establishing connectivity among the populations of various shark species is important to determine the appropriate units and spatial scale for conservation and management, particularly as this group is long-lived with late age of maturation. Consequently, we used DNA variation at 1,317 putatively neutral and 25 potentially adaptive single nucleotide polymorphisms (SNPs) to analyze population genetic structure among 174 unrelated individuals of scalloped hammerhead sharks (Sphyrna lewini) from the Rewa Delta and the Ba Estuary, where documented aggregations of neonates and young-of-the-year occur in the island of Viti Levu, Republic of Fiji. Results of the pairwise FST analysis for the neutral loci revealed a small but significant genetic differentiation (FST: 0.004; P-value = 0.0009). Furthermore, the 25 potentially adaptive loci (i.e. under putative selection) revealed a magnitude of differentiation four times bigger than the estimate obtained using neutral genetic diversity (FST: 0.017; P-value = 0.0009). Interestingly, population assignment tests, using the neutral SNP data set and two different software packages, Admixture and assignPOP, provided evidence for the existence of up to four genetically differentiated populations among our samples. Assignment probabilities ranged from 0.98 ± 0.01 to 0.81 ± 0.03. Admixture and assignPOP assigned the same individuals to the same putative populations for all sampled neonates. Thus, our results provide unequivocal evidence that adult females from multiple genetically differentiated breeding populations contribute to these juvenile aggregation sites.

Keywords: Scalloped hammerhead shark, population genetic structure, genetic diversity, single nucelotide polymorphisms, kinship relationships, Adaptive divergence, admixture

Received: 25 Jul 2019; Accepted: 06 Nov 2019.

Copyright: © 2019 Marie, Stockwell and Rico. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Ciro Rico, University of the South Pacific, Suva, Fiji, ciro.rico@usp.ac.fj