Genetic characterization of green turtles (Chelonia mydas) from São Tomé and Príncipe: Insights on species recruitment and dispersal in the Gulf of Guinea

Abstract

Genetic 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.