Browsing by Author "Hancock, Joana M."
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- Atlantic connectivity of a major green sea turtle Chelonia mydas foraging aggregation at the Banc d’Arguin, MauritaniaPublication . Patrício, Ana Rita; Coveney, Sophia A.; Barbanti, Anna; Barbosa, Castro; Broderick, Annette; El’Bar, Nahi; Godley, Brendan; Hancock, Joana M.; Regalla De Barros, Aissa; Senhoury, Cheibani; Sidina, Ebaye; de Thoisy, Benoît de; Tilley, Dominic; Weber, Sam; Catry, PauloABSTRACT: Understanding population connectivity is paramount for effective conservation. While genetic tools have elucidated sea turtle migration patterns, notable data gaps limit our understanding of ocean-wide connectivity, especially regarding east Atlantic green turtles. We characterized the genetic composition of a globally important green turtle foraging aggregation at the Banc d’Arguin, Mauritania, incorporating data from 323 individuals captured between 2018 and 2021. Using extended mitochondrial DNA D-loop (738 base pairs [bp]) and mitochondrial short tandem repeat (mtSTR; ~200 bp) markers, we assessed the genetic structure of Atlantic green turtle foraging aggregations and estimated the most likely origin of immature green turtles from the Banc d’Arguin using mixed stock analyses (MSAs). We identified 6 D-loop haplotypes, with a clear dominance of CM-A8.1 (91.8%) followed by CM-A5.1 (6.3%) and 4 rare haplotypes: CM-A1.4, CMA6.1, CM24.1 and CM36.1. We found 13 mtSTR haplotypes, with ‘7-12-4-4’ being dominant (89.0%). The genetic composition at the Banc d’Arguin differed significantly from the only foraging aggregation studied in West Africa to date — in the archipelago of Cabo Verde (located ca. 750 km from the Banc d’Arguin) — dominated by haplotype CM-A5. The MSA combining both genetic markers indicated that 87.6% of immature green turtles at the Banc d’Arguin originate from the major East Atlantic rookery at Poilão (Guinea-Bissau), but 11.6% come from more distant rookeries in South America (8.1%) and potentially Ascension Island (3.4%). We suggest that green turtle transatlantic movements may be more common than previously thought and highlight the importance of the Banc d’Arguin as a regional foraging hub for this species.
- Genetic characterization of green turtles (Chelonia mydas) from São Tomé and Príncipe: Insights on species recruitment and dispersal in the Gulf of GuineaPublication . Hancock, Joana M.; Vieira, Sara; Taraveira, Lúcio; Santos, Aladino; Schmitt, Vanessa; Semedo, Alcides; Patrício, Ana Rita; Ferrand, Nuno; Gonçalves, Helena; Sequeira, FernandoGenetic studies on green sea turtles (Chelonia mydas) in the Eastern Atlantic have mostly focused on reproductive females, with limited information available regarding juveniles and foraging grounds. Improved understanding of genetic diversity and patterns of connectivity between nesting and foraging grounds is critical to identify management units and delineate suitable conservation strategies. Here we analyzed data from 11 microsatellite markers and sequences of the mitochondrial control region from both juveniles and females sampled in foraging and nesting aggregations around São Tomé and Príncipe islands, in the Gulf of Guinea, West Africa. Both nuclear and mtDNA data were congruent in showing that São Tomé and Príncipe's green turtles population exhibit high levels of genetic diversity, which are similar to those reported for other foraging aggregates in the Atlantic. Although signs of population substructure among foraging and nesting grounds of São Tomé and Príncipe islands were not apparent, our analysis based on mtDNA marker showed that both juvenile and adult turtles were genetically differentiated from other foraging and nesting Atlantic populations. The similar levels of genetic diversity found in both juveniles and females are consistent with the results from mixed stock analyses, which suggested that São Tomé and Príncipe's rookery is the primary source of juveniles to the local foraging aggregation. Taken these aspects in consideration, we argue that São Tomé and Príncipe green turtles show limited dispersal and should be considered an important management unit, and conservation actions in this archipelago must be implemented not only at the level of the rookery but should also include the foraging aggregations.