Reviewing the genetic evidence for sex-biased dispersal in elasmobranchs

Phillips, Nicole M.; Devloo‐Delva, Floriaan; McCall, C. I.; Daly‐Engel, Toby S.

doi:10.1007/s11160-021-09673-9

Cited by 21 publications

(23 citation statements)

References 129 publications

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“…Indeed, pooling of life stages, i.e. across sizes, during data analysis can obscure estimates of stock structure and dispersal 65 . This is, however, unlikely to be an issue in our study because we were able to identify clear stock structure regardless of the majority of our samples being from large tiger sharks known to be the most dispersive 54 , 57 , 64 .…”

Section: Discussionmentioning

confidence: 99%

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Manuzzi

Jiménez‐Mena

Henriques

et al. 2022

Sci Rep

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Over the last century, many shark populations have declined, primarily due to overexploitation in commercial, artisanal and recreational fisheries. In addition, in some locations the use of shark control programs also has had an impact on shark numbers. Still, there is a general perception that populations of large ocean predators cover wide areas and therefore their diversity is less susceptible to local anthropogenic disturbance. Here we report on temporal genomic analyses of tiger shark (Galeocerdo cuvier) DNA samples that were collected from eastern Australia over the past century. Using Single Nucleotide Polymorphism (SNP) loci, we documented a significant change in genetic composition of tiger sharks born between ~1939 and 2015. The change was most likely due to a shift over time in the relative contribution of two well-differentiated, but hitherto cryptic populations. Our data strongly indicate a dramatic shift in the relative contribution of these two populations to the overall tiger shark abundance on the east coast of Australia, possibly associated with differences in direct or indirect exploitation rates.

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Section: Discussionmentioning

confidence: 99%

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Manuzzi

Jiménez‐Mena

Henriques

et al. 2022

Sci Rep

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“…Conversely, high vagility can maintain gene flow over global scales when reproduction accompanies physical movement (Chapman et al, 2015). In highly vagile sharks, studies have found more fine-scale genetic structure than expected, a pattern that is regularly attributed to female natal philopatry (when females return to their own birthplace to reproduce), a type of reproductive investment (Chapman et al, 2015;Phillips et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…The pattern for males based on tagging data is less clear, with tagged males exhibiting regional philopatry but limited association with pupping habitats (Hammerschlag et al, 2011). While tagging data can shed valuable light on reproductive behavior, patterns of reproductive dispersal and the impact on regional diversity must be verified by examining patterns of gene flow between populations (reviewed in Phillips et al, 2021). Often, data from biparentally-inherited nuclear genes (nDNA) is compared with maternally-inherited mitochondrial genes (mtDNA), with reproductive philopatry indicated by significant structure between regions at one marker type (Goudet et al, 2002;Phillips et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Genetic studies on sharks have regularly shown significant mtDNA structure with contrasting panmixia at nDNA, which is commonly interpreted as female natal philopatry against a background of basin-wide male dispersal (Daly-Engel et al, 2012;Veríssimo et al, 2012;Phillips et al, 2021). This contrasting pattern of female philopatry against a background of male-biased dispersal is now the prevailing view for many sharks, including large species with global ranges (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…But this ignores the fact that most sharks undergo an ontogenetic shifts that causes their movement patterns to change at a specific point in their development (Grubbs, 2010), such that the possibility of an animal being a non-reproducing migrant appears only after this shift. The result is a mixed assemblage of non-migratory juvenile and migratory subadult and adult sharks, which when analyzed together may incorrectly present as evidence of genetic panmixia (Phillips et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

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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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Baseline genetic distinctiveness supports structured populations of thornback ray in the Mediterranean Sea

Melis

Vacca

Cariani

et al. 2023

Aquatic Conservation

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1. The thornback ray (Raja clavata) is the most important chondrichthyan in terms of landings in the Mediterranean Sea. Intense harvesting may induce negative genetic effects reducing the resilience of overfished species. For this reason, genetic diversity information should be considered in fisheries management and conservation policies.2. Microsatellite markers were used to unravel the genetic features (variability, connectivity, sex-biased dispersal) of R. clavata populations, both at the small (around the coast of Sardinia, western Mediterranean Sea) and larger spatial scales (at the pan-Mediterranean level, and between the Atlantic Ocean and the Mediterranean Sea).3. Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences between Mediterranean and Atlantic rays, as well as within the Mediterranean Sea between its western and eastern basins. The data indicated that both the Strait of Gibraltar and the Sicilian Channel seem to be effective in limiting the dispersal of thornback ray individuals, but a further structuring was identified, with the significant genetic differentiation of the populations located in the Algero-Provençal and Tyrrhenian basins. Such a fine-scale arrangement suggests the occurrence of additional barriers to species dispersal. A lack of significant genetic differentiation, stable over the years, was measured at a local scale among R. clavata Sardinian samples. 4. Several possible mechanisms, both biological and abiotic (e.g. migratory behaviour, waterfronts and oceanographic discontinuities), are discussed. Overall, the genetic data presented, both at the local and regional level, could represent the baseline information for the temporal monitoring of populations and assessing the effects of present or future fisheries-related management actions.Riccardo Melis and Laura Vacca share first authorship.

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Reviewing the genetic evidence for sex-biased dispersal in elasmobranchs

Cited by 21 publications

References 129 publications

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population

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

Baseline genetic distinctiveness supports structured populations of thornback ray in the Mediterranean Sea

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