Nuclear genetic structure of the white shark (Carcharodon carcharias) from the Northeastern Pacific

Abstract

The Northeastern Pacific (NEP) population of white sharks (Carcharodon carcharias) is genetically distinct from the rest of the world. This uniqueness results from adult fidelity to central California and Guadalupe Island aggregations sites. The strong mitochondrial genetic structure between the white sharks of central California and Guadalupe Island is also present, which indicates female philopatry. To date, few studies using nuclear DNA have found evidence of genetic patterns in the NEP white shark population, which could indicate that these sharks exhibit sex-biased dispersal. In this study, we evaluated the genetic structure, connectivity, and genetic diversity of NEP white sharks using samples from the southern California Bight (SCB), Baja California (including Sebastian Vizcaino Bay), the Gulf of California, and Guadalupe Island (GI) using nDNA (i.e. microsatellite loci). A total of five loci were successfully genotyped in 54 individuals. The patterns found in this study indicated low levels of genetic diversity among all localities (observed heterozygosity: Ho = 0.47), likely due to a founder effect. A slight genetic structure was present for NEP localities in this study (FST = 0.045, P = 0.0001), mainly identified between the SCB and GI locations. A sibship assignment analysis indicated low and moderate probabilities of full- and half-siblings between white shark juveniles from coastal areas, suggesting a high degree of connectivity between nursery areas in the NEP. Our results suggest that juveniles can mask the genetic structure in coastal zones.