Restricted connectivity and population genetic fragility in a globally endangered Hammerhead Shark

Pinhal, Danillo; Domingues, Rodrigo Rodrigues; Bruels, Christine C.; Ferrette, Bruno Lopes da Silva; Gadig, Otto Bismarck Fazzano; Shivji, Mahmood S.; Martins, Cesar

doi:10.1007/s11160-020-09607-x

Cited by 23 publications

(32 citation statements)

References 88 publications

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“…Therefore, it is concluded that S. zygaena is composed of six populations worldwide, three within the Atlantic Ocean one in the South‐west Atlantic and two in the Eastern Central Atlantic, – one in the South‐west Indian Ocean, and two in the Pacific Ocean, one each in the western and eastern portions. These results evidence that the phylogeographic population structure of S. zygaena is higher than for other species of the family Sphyrnidae, such as S. lewini (Duncan et al, 2006; Pinhal et al, 2020) and S. tiburo (Escatel‐Luna et al, 2015; Fields et al, 2016), evidencing a lower gene flow among distant geographical regions that could imply a need to assume different management units for the conservation of the species across its distribution range.…”

Section: Discussionmentioning

confidence: 72%

“…This study is the most extensive genetic evaluation for S. zygaena to date and the first to examine the Atlantic Ocean genetic population structure. Compared with other Sphyrnidae studies using the same molecular markers, S. zygaena has lower overall genetic diversity than S. lewini (Duncan et al, 2006; Pinhal et al, 2020) and S. tiburo (Escatel‐Luna et al, 2015; Fields et al, 2016) but higher than for S. tudes (Tavares et al, 2013). Sphyrna zygaena in the Atlantic Ocean exhibit similar genetic diversity to those in the Eastern Pacific (Bolaño‐Martínez et al, 2019), although S. zygaena in the northern Mexican Pacific region exhibit lower genetic diversity (Félix‐López et al, 2019).…”

Section: Discussionmentioning

confidence: 73%

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Global phylogeography of the smooth hammerhead shark: Glacial refugia and historical migration patterns

Ferrette

Coelho

Peddemors

et al. 2021

Aquatic Conservation

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1. Extreme climate changes during the Cenozoic Era strengthened different biogeographical barriers that decreased the connectivity among populations, triggering lineage diversification of different species worldwide. 2. The mitochondrial DNA control region was employed to explore the phylogeography of Sphyrna zygaena, a globally distributed species threatened by unsustainable, illegal, unreported and unregulated fisheries triggered by the international shark fin trade. It is listed as 'Vulnerable' by the IUCN Red List and its trade is regulated by CITES Appendix II. 3. Only 13 haplotypes were found with low genetic diversity levels (hd = 0.686 ± 0.014; π = 0.00206 ± 0.00004) compared with other species of the Sphyrnidae family. The species has a very strong phylogeographic population structure among the Atlantic, Indian and Pacific Oceans (Φ ST = 0.79132).Worldwide, there are six distinct populations with some haplotype sharing.4. These populations are probably connected by a stepping-stone dispersal of a small number of migrants per generation from the Indo-Pacific towards the Atlantic. Modelling suggests that S. zygaena diverged into two lineages around 6.96 million years ago which have been isolated in glacial refuges in the Atlantic and Indo-Pacific oceans; and after deglaciation, a population expansion probably permitted secondary contact. 5. Conservation plans to establish differentiated management units should be adopted in each of the identified populations. Among these, the Eastern Central Atlantic and West Indo-Pacific are the most important areas for the species considering the historical migration routes that act as a bridge connecting the Atlantic and Indo-Pacific Oceans while the Gulf of Guinea connects the Atlantic populations. Still, further studies are required to know if these populations are also linked with nursery areas for the species.6. The results herein can help to delimit the main evolutionarily significant units to implement effective policies to establish differentiated management units as starting points to genetic monitoring programmes for Sphyrna zygaena.

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 73%

Global phylogeography of the smooth hammerhead shark: Glacial refugia and historical migration patterns

Ferrette

Coelho

Peddemors

et al. 2021

Aquatic Conservation

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“…typus give rise to many questions for which studies including tagging with acoustic transmitters [e.g. 68 ] and genetic analyses [ 69 , 70 ] will provide information about (i) their residence time at Europa with eventual site-fidelity, migration paths, and eventually including deep incursions at Hall Table mount and Jaguar Seamount, as well as (ii) their population structure, in particular in the Mozambique Channel. This knowledge is needed for adjusting to its behavior the conservation of these poorly known and endangered species as recorded on the CITES list.…”

Section: Discussionmentioning

confidence: 99%

Observations of sharks (Elasmobranchii) at Europa Island, a remote marine protected area important for shark conservation in the southern Mozambique Channel

Guillaume

Séret²

2021

PLoS ONE

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Sharks have declined worldwide and remote sanctuaries are becoming crucial for shark conservation. The southwest Indian Ocean is a hotspot of both terrestrial and marine biodiversity mostly impacted by anthropogenic damage. Sharks were observed during surveys performed from April to June 2013 in the virtually pristine coral reefs around Europa Island, a remote Marine Protected Area located in the southern Mozambique Channel. Observation events comprised 67 1-hour scientific dives between 5 – 35m depth and 7 snorkeling inspections, as well as 4 dinghy-based observations in the shallow lagoon. In a period of 24 days, 475 sharks were tallied. Carcharhinus galapagensis was most encountered and contributed 20% of the abundance during diving, followed by C. albimarginatus (10%). Both species were more abundant between 11-14h, and on the exposed sides of the island. Numbers of Sphyrna lewini were highest with 370 individuals windward and leeward, mostly schooling. S. lewini aggregations in the area are hypothesized to be attracted to the seamount archipelago offering favorable conditions for deep incursions and of which Europa Island forms part. C. amblyrhynchos, Galeocerdo cuvier and S. mokarran were uncommon, while there was an additional observation of Rhincodon typus. The lagoon of Europa was a nursery ground for C. melanopterus where it was the only species present. A total of 8 species was recorded, contributing to the shark diversity of 15 species reported from Europa since 1952 in the scientific and gray literature. Overall, with the occurrence of several species of apex predators in addition to that of R. typus, large schools of S. lewini, fair numbers of reef sharks and a nursery of C. melanopterus, Europa’s sharks constitute a significant reservoir of biodiversity, which contributes to preserve the functioning of the ecosystem. Our observations highlight the relevance of Europa Island for shark conservation and the need for shark-targeted management in the EEZ of both Europa and Bassas da India.

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“…To complement previous population structure analysis, a multivariate approach, Discriminant Analysis of Principal Components (DAPC) (62) was used to identify discrete populations based on geographic region, using the Adegenet package in R v.4.0.2. The DAPC summarizes initial genetic data into uncorrelated groups using principal components, then uses discriminant analysis to maximize the among-population variation (63). Cluster assignments were pre-defined corresponding with defined collection locations.…”

Section: Microsatellite Dna Data Analysismentioning

confidence: 99%

“…lewini is reproductive philopatric behavior rather than oceanographic or geophysical barriers (Pinhal et al, 2020).…”

Section: Relatedness and Natal Philopatrymentioning

confidence: 99%

Population structure and genetic connectivity of the scalloped hammerhead shark (Sphyrna lewini) across nursery grounds from the Eastern Tropical Pacific: implications for management and conservation

Elizondo-Sancho

Rodríguez-Arriatti²,

Albertazzi

et al. 2022

Preprint

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Defining demographically independent units and understanding gene flow between them is essential for managing and conserving exploited populations. The scalloped hammerhead shark, Sphyrna lewini, is a coastal semi-oceanic species found worldwide in tropical and subtropical waters. Pregnant females give birth in shallow coastal estuarine habitats that serve as nursery grounds for neonates and small juveniles, and adults move offshore and become highly migratory. We evaluated the population structure and connectivity of S. lewini in coastal areas across the Eastern Tropical Pacific (ETP) using both sequences of the mitochondrial DNA control region (mtCR) and nuclear-encoded microsatellite loci. The mtCR defined two genetically discrete geographic groups: the Mexican Pacific and the central-southern Eastern Tropical Pacific (Guatemala, Costa Rica, Panamá, and Colombia). Overall, the mtCR data showed low levels of haplotype diversity ranged from 0.000 to 0.608, while nucleotide diversity ranged from 0.000 to 0.0015. A more fine-grade population structure analysis was detected using microsatellite loci where Guatemala, Costa Rica, and Panamá differed significantly. Genetic diversity analysis with nuclear markers revealed an observed heterozygosity ranging from 0.68 to 0.71 and an allelic richness from 5.89 to 7.00. Relatedness analysis revealed that individuals within nursery areas were more closely related than expected by chance, suggesting that S. lewini may exhibit reproductive philopatric behaviour within the ETP. Findings of at least two different management units, and evidence of philopatric behaviour call for intensive conservation actions for this critically endangered species in the ETP.

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Restricted connectivity and population genetic fragility in a globally endangered Hammerhead Shark

Cited by 23 publications

References 88 publications

Global phylogeography of the smooth hammerhead shark: Glacial refugia and historical migration patterns

Global phylogeography of the smooth hammerhead shark: Glacial refugia and historical migration patterns

Observations of sharks (Elasmobranchii) at Europa Island, a remote marine protected area important for shark conservation in the southern Mozambique Channel

Population structure and genetic connectivity of the scalloped hammerhead shark (Sphyrna lewini) across nursery grounds from the Eastern Tropical Pacific: implications for management and conservation

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