Advancing Genetic Stock Identification of Leatherback Turtles From Foraging Grounds in the Southwest Atlantic: Insights From Nuclear DNA ( nDNA ) Analysis

Abstract

The leatherback turtle (Dermochelys coriacea) undertakes extensive migrations between nesting and foraging areas, where it isexposed to threats such as fisheries bycatch, coastal development, and pollution. Although classified globally as Vulnerable bythe IUCN, the Southwest Atlantic subpopulation is considered Critically Endangered, with nesting restricted to Brazil. Whilesatellite telemetry and previous mitochondrial DNA (mtDNA) Genetic Mixed Stock Analysis (MSA) studies have indicated thatleatherbacks from West African rookeries migrate to foraging grounds off Argentina and Uruguay, the potential for connectivitywith rookeries from other regions remains an open question. Genetic Stock Identification (GSI) using 15 nuclear DNA (nDNA)microsatellite markers was conducted on 78 stranded or incidentally caught leatherbacks from feeding grounds off the coasts ofArgentina and Uruguay. Assignment analysis results demonstrated that 92% of the foraging leatherbacks originated from Ghanaand Gabon in the Southeast Atlantic (SEA), with lesser contributions from the rookeries in the Northwest Atlantic (NEA; 6%)and the Southwest Indian Ocean (SWI; 1%) rookery in South Africa, all with assignment probabilities (AP) exceeding 95%. Ourfindings corroborate and extend previous mtDNA studies by enhancing the precision of GSI for individuals possessing commonhaplotypes and by clarifying the unknown origin of individuals with ‘orphan’ mtDNA haplotypes, such as Dc7.1, which wereassigned to the SEA rookeries (AP = 99%). Furthermore, we directly assigned one individual, previously of uncertain mtDNAorigin (Dc9.1), to the South Africa rookery (AP = 97%), highlighting the need to consider the extension of the SWI RegionalManagement Unit (RMU) boundaries to Southwest Atlantic waters in future assessments. The absence of detected connectivitywith Brazilian nesting populations underscores the necessity for increased sample sizes and the application of advanced molecu-lar markers. These results advance the understanding of population connectivity across oceanic scales and emphasize the crucialrole of international collaboration in conservation endeavors.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium,provided the original work is properly cited.© 2026 NGO Karumbe and The Author(s). Ecology and Evolution published by British Ecological Society and John Wiley & Sons Ltd. This article has been contributedto by U.S. Government employees and their work is in the public domain in the USA.L.P. and S.E.R should be considered joint first authors.