A new map of the tiger shark (Galeocerdo cuvier) genetic population structure in the western Atlantic Ocean: Hypothesis of an equatorial convergence centre

Abstract

1. The tiger shark (Galeocerdo cuvier) is a common widespread coastal-pelagic shark species whose population genetic structure has only recently been the object of genetic studies.2. In this study, the tiger's shark mitochondrial DNA control region was sequenced for a sample of 172 individuals from the western Atlantic and from Australia's east coast in the Pacific Ocean.3. The results show a moderate variation in genetic diversity (h = 0.615 ± 0.038, π = 0.00184 ± 0.00021) with a strong population structure between Atlantic areas (Φ ST = 0.28141, P = 0.00001).4. The maternal lineage has high site fidelity, which paradoxically is coupled with connectivity across open ocean stretches to Fernando de Noronha Archipelago, which is identified as an important hotspot for this species. These results help with the understanding of what drives the displacement of this shark, at intra-and/or inter-ocean basins levels, and can help inform the implementation of future conservation and management measures.5. We recommend that the conservation of genetic diversity should be maintained at a global level and its maintenance should be pursued diligently in all populations of tiger shark. As the Fernando de Noronha region in the western Atlantic appears to contain the largest global genetic diversity of the species, this area should be treated as a marine reserve or ecological refuge for the tiger shark.

Population genetics reveals global and regional history of the apex predator Galeocerdocuvier (carcharhiniformes) with comments on mitigating shark attacks in north‐eastern brazil

“…Thereby, such evidences suggest a subtle division in the genetic variation between Pernambuco (MRR + FN) and South-eastern Brazil. This hypothesis reinforced partially the original idea of a barrier occurring between FN Islands and South-eastern Brazil (Carmo et al, 2019). On the other hand, the results obtained In conclusion, using the overall set of findings and hypotheses found in this study it is possible to reinforce that Galeocerdo cuvier is regionally and globally resilient based on the moderate to eventually high levels of genetic diversity.…”

“…This comparison suggests that G. cuvier present similar values to other species. suggesting that the FN population contributed significantly to the magnitude of tiger shark genetic variation in the region, reinforcing the importance of the region for conservation (Carmo et al, 2019).…”

“…The sequences obtained were aligned using the Clustal W programme (Thompson et al, 1994), implemented on BioEdit (Hall, 1999), visually edited, and the gaps were treated as missing data. The CR data were incremented with the addition of 28 more tiger shark sequences from various areas, made available by Pirog et al (2015), Bernard et al (2016) and Carmo et al (2019). These data were discriminated here using the following abbreviations:…”

“…Population genetics have been studied for sharks, such as blacktip sharks ( Carcharhinus limbatus Müler & Henle, 1839) (Keeney & Heist, 2006), blue sharks ( Prionace glauca Linneaus, 1758) (Veríssimo et al., 2017), whale sharks ( Rhincodon typus Smith, 1828) (Castro et al., 2007; Sigsgaard et al., 2016), great white sharks ( Carchardodon carcharias Linnaeus, 1758) (Blower et al., 2012; Gubili et al., 2010, 2015) and tiger sharks ( Galeocerdo cuvier Péron & Lesueur, 1822) (Carmo et al., 2019; Pirog et al., 2019), the target species of this paper.…”

“…Genetic data for G. cuvier from different parts of the world have revealed a better condition of the species in adaptive terms, considering the values of genetic diversity observed in mitochondrial and nuclear regions (Bernard et al., 2016; Carmo et al., 2019). Recently, this species has presented moderate genetic diversity estimates and strong genetic structuring from samples from the Atlantic and the Pacific (Carmo et al., 2019; Pirog et al., 2019). The Archipelago of Fernando de Noronha (FN) has also been suggested as a refuge zone for the conservation of the species, considering the high degree of genetic diversity in this area (Carmo et al., 2019).…”