Population structure and connectivity of tiger sharks (Galeocerdo cuvier) across the Indo-Pacific Ocean basin

Abstract

Population genetic structure using nine polymorphic nuclear microsatellite loci was assessed for the tiger shark (Galeocerdo cuvier) at seven locations across the Indo-Pacific, and one location in the southern Atlantic. Genetic analyses revealed considerable genetic structuring (FST > 0.14, p < 0.001) between all Indo-Pacific locations and Brazil. By contrast, no significant genetic differences were observed between locations from within the Pacific or Indian Oceans, identifying an apparent large, single Indo-Pacific population. A lack of differentiation between tiger sharks sampled in Hawaii and other Indo-Pacific locations identified herein is in contrast to an earlier global tiger shark nDNA study. The results of our power analysis provide evidence to suggest that the larger sample sizes used here negated any weak population subdivision observed previously. These results further highlight the need for cross-jurisdictional efforts to manage the sustainable exploitation of large migratory sharks like G. cuvier.

Genetic population structure and demography of an apex predator, the tiger shark Galeocerdo cuvier

“…Microsatellite genotypes generated by Holmes et al. () and Bernard et al. () were also added to the present study (Figure ; Table ).…”

“…Using nine microsatellite loci, Holmes et al. () confirmed genetic isolation between the western Atlantic and the Indo‐Pacific. Further, the high connectivity around Australia found by Bernard et al.…”

“…Recorded differences between the west and east coast of Australia were hypothesized to be a result of a stronger matrilineal structure due to sex‐biased dispersal and female philopatry. An additional study focused on the population structure of tiger sharks across the eastern Indian Ocean and the Pacific, with 355 samples collected primarily around Australia and Hawaii, with eight samples from Brazil in the southwest Atlantic as an outgroup (Holmes et al., ). Using nine microsatellite loci, Holmes et al.…”

“…As we used samples in common with Holmes et al. () and the nine microsatellite loci they used, we were able to combine samples to obtain a more precise picture of the population genetic dynamics of the tiger shark in the Indo‐Pacific. In addition, CR sequences obtained by Bernard et al.…”

Genetic connectivity and phylogeography of the night shark (Carcharhinus signatus) in the western Atlantic Ocean: Implications for conservation management

“…Many species that are widely distributed and highly vagile exhibit little population structure and constitute a single panmictic population (Graves, 1998); however, previous studies of shark population structure have shown significant genetic subdivision at global (e.g. Bernard et al, 2016;Clarke et al, 2015) and regional scales (Domingues, Hilsdorf, Shivji, Hazin, & Gadig, 2018;Holmes et al, 2017;Karl et al, 2011;Karl, Castro, & Garla, 2012). Indeed, sharks have been the focus of many studies on migration and site fidelity, using traditional methods such as capture-tagging-recapture and acoustic tracking (e.g.…”