Population genetics reveals global and regional history of the apex predator <i>Galeocerdo</i><i>cuvier</i> (carcharhiniformes) with comments on mitigating shark attacks in north‐eastern brazil

Andrade, Flávia R.S.; Afonso, André S.; Hazin, Fábio Hissa Vieira; Mendonça, Fernando Fernandes; Torres, Rodrigo A.

doi:10.1111/maec.12640

Cited by 8 publications

(7 citation statements)

References 134 publications

(182 reference statements)

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“…Even though more sampling sites and SNPs would likely have provided tighter estimates, this result is most consistent with a single mating population in the AO, despite our single sampling site does not allow us to infer the geographic extent of that population. We note that population structure has previously been reported within the AO based on mitochondrial markers [ 25 , 26 ]. However, results in the current study are consistent with the genome wide study of [ 27 ] which suggested low to no population structure in the AO.…”

Section: Discussionsupporting

confidence: 56%

“…The strong signature of population expansion recovered implies that the tiger shark is profiting from recent environmental changes in AO, in contrast to the IP population. Consistently, [ 26 , 48 ] found a recent demographic trend suggesting an expansion rather than a decrease in AO, while the recent demographic trends in the IP appear to have been the result of intense pressure from fisheries and shark-control programs [ 9 – 11 ]. More investigations are needed to determine the origin of the difference between the two oceans.…”

Section: Discussionmentioning

confidence: 85%

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Ecological and biogeographic features shaped the complex evolutionary history of an iconic apex predator (Galeocerdo cuvier)

et al. 2022

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Background The tiger shark (Galeocerdo cuvier) is a large iconic marine predator inhabiting worldwide tropical and subtropical waters. So far, only mitochondrial markers and microsatellites studies have investigated its worldwide historical demography with inconclusive outcomes. Here, we assessed for the first time the genomic variability of tiger shark based on RAD-seq data for 50 individuals from five sampling sites in the Indo-Pacific (IP) and one in the Atlantic Ocean (AO) to decipher the extent of the species’ global connectivity and its demographic history. Results Clustering algorithms (PCA and NMF), FST and an approximate Bayesian computation framework revealed the presence of two clusters corresponding to the two oceanic basins. By modelling the two-dimensional site frequency spectrum, we tested alternative isolation/migration scenarios between these two identified populations. We found the highest support for a divergence time between the two ocean basins of ~ 193,000 years before present (B.P) and an ongoing but limited asymmetric migration ~ 176 times larger from the IP to the AO (Nm ~ 3.9) than vice versa (Nm ~ 0.02). Conclusions The two oceanic regions are isolated by a strong barrier to dispersal more permeable from the IP to the AO through the Agulhas leakage. We finally emphasized contrasting recent demographic histories for the two regions, with the IP characterized by a recent bottleneck around 2000 years B.P. and the AO by an expansion starting 6000 years B.P. The large differentiation between the two oceanic regions and the absence of population structure within each ocean basin highlight the need for two large management units and call for future conservation programs at the oceanic rather than local scale, particularly in the Indo-Pacific where the population is declining.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 85%

Ecological and biogeographic features shaped the complex evolutionary history of an iconic apex predator (Galeocerdo cuvier)

et al. 2022

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Section: Discussionmentioning

confidence: 99%

“…Although tiger sharks exhibit a circumglobal distribution in both tropical and temperate waters, information on population connectivity, dynamics and genetic structure, only began to be unraveled in the last decade ( Andrade et al, 2021 ; Bernard et al, 2016 ; Carmo et al, 2019 ). The studies retrieved herein indicate confirmed genetic differentiation between tiger sharks from the West Atlantic, North Atlantic, and Southwest Atlantic, and an isolated population identified in Hawaii ( Andrade et al, 2021 ; Bernard et al, 2016 ). Studies indicate that the separation between Indo-Pacific and West Atlantic populations took place only about 1 million years ago, with the Southwest Atlantic serving as a connection point between ocean basins, allowing for population breeding through incursions along the South African tip ( Bernard et al, 2016 ).…”

Section: Discussionmentioning

confidence: 99%

Almost nothing is known about the tiger shark in South Atlantic waters

Balanin

Hauser‐Davis

Giareta

et al. 2023

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The tiger shark (Galeocerdo cuvier) has been relatively well assessed concerning biology and ecology aspects in both Atlantic and Pacific North America and in Caribbean waters. The amount of data in these regions has led to the species protection under capture quotas and with the creation of sanctuaries. The reality in developing countries, however, is the exact opposite, with scarce information on the species in the southern hemisphere, namely South American and African waters. In these regions, protection measures are insufficient, and studies on tiger shark biology and ecology are scarce, significantly hindering conservation and management efforts. Thus, the aim of this study was to compile scientific literature on the tiger shark in the South Atlantic and discuss the impact of these data (or lack thereof) distributed within a total of ten research categories for guiding management plans. In total, 41 scientific publications on different G. cuvier biology and ecology aspects were obtained. The most studied topics were Feeding Ecology (n = 12), followed by Human Interactions (n = 8), and Movements and Migration (n = 7). Northeastern Brazil (Southwest Atlantic) was the most researched area, probably due to the higher coastal abundance of tiger sharks in this area, alongside a high number of recorded attacks, justifying funding for studies in the region. No studies carried out in other South American or African countries were found. It is important to mention that even though some research topics are relatively well covered, a severe knowledge gap is noted for risk assessments and fisheries management, with a proposition for the implementation of sanctuaries noted. This is, however, particularly worrisome, as the South Atlantic is mostly unexplored in this regard for tiger sharks. It is also important to note how different the attention given to this species is in the North Atlantic when compared to the South region. Lastly, we highlight that the existence of sub-populations, the lack of migratory corridors geographically connecting distinct areas used by the species, and the lack of fisheries statistics on tiger shark landings, all increase the vulnerability of this species in the South Atlantic.

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“…In contrast, genetic data on the same populations have consistently shown fine-scale structure attributed to malebiased dispersal and female philopatry (Bernard et al, 2016;Carmo et al, 2019). Global genetic studies have shown deep evolutionary partitioning in tiger sharks between the Atlantic and Indo-Pacific, but biparental structure within basins is largely absent (Bernard et al, 2016;Pirog et al, 2019;Andrade et al, 2021;Bernard et al, 2021). Though no studies have examined the effect of size class, previous genetic work on tiger sharks in the northwest Atlantic identified structure at maternally-inherited mitochondrial DNA, including a divergent lineage located in the Caribbean (Carmo et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Age-Dependent Dispersal and Relatedness in Tiger Sharks (Galeocerdo cuvier)

et al. 2022

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Understanding dispersal in large marine fauna is necessary for conservation, but movement patterns often vary widely by sex and life stage. In sharks, genetic studies have shown evidence of widespread male-biased dispersal, though tagging and tracking studies on the same populations show both sexes using site fidelity, including philopatry, and moving similar distances. We used a suite of microsatellite loci and DNA samples from 362 previously-tagged tiger sharks (Galeocerdo cuvier) in the northwestern Atlantic, including a large number of residential juveniles, to evaluate reproductive dispersal in light of demographic and published tracking data. We found that lumping size classes together resulted in genetic panmixia across sites, but systematic removal of large individuals showed significant population-level differentiation and three separate population clusters among juveniles less than 260 cm total length. Tests for relatedness found that 8.9% of our sample set was composed of first-order related pairs (N = 16), including several full siblings from different litters, a sign of multi-cycle genetic monogamy which carries implications for effective population size. By mapping genetic assignments of juveniles, we identified a signature of fine-scale genetic structure suggesting broad biparental site fidelity to reproductive habitat in the northeast Gulf of Mexico, which is concordant with both genetic and tracking data. Taken together, these findings demonstrate how lumping individuals from different life stages in genetic studies may obscure fine-scale genetic structure, confounding future conservation efforts.

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

Abstract: The understanding of the population genetic structure of the species is of great importance because it reveals information about the geographic limits of populations by analysing the gene flow between locations. This approach can be also used as possible drivers for their conservation (

Cited by 8 publications

References 134 publications

Ecological and biogeographic features shaped the complex evolutionary history of an iconic apex predator (Galeocerdo cuvier)

Ecological and biogeographic features shaped the complex evolutionary history of an iconic apex predator (Galeocerdo cuvier)

Almost nothing is known about the tiger shark in South Atlantic waters

Age-Dependent Dispersal and Relatedness in Tiger Sharks (Galeocerdo cuvier)

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