Genetic monitoring of the critically endangered leatherback turtle (Dermochelys coriacea) in the South West Atlantic

Although leatherback turtles (Dermochelys coriacea) are highly migratory and have a wide oceanic distribution, the South West Atlantic (SWA) subpopulation comprises few reproductive females and is listed as Critically Endangered. Herein, we present temporal genetic assessment of the poorly known subpopulation of the D. coriacea from SWA subpopulation. A total of 39 leatherback adult individuals were sampled during seven reproduction seasons along 160 km in the main nesting area in Brazil and analysed using D-loop mtDNA sequences (N = 37) and 25 microsatellite loci (N = 29). We detected genetic differences in temporal mtDNA analysis, possible explained by genetic drift. We also found two different genetic clusters with admixture between them for SWA subpopulation, indicating possible gene flow between different nesting areas. The SWA subpopulation presented low mean number of different alleles, moderate levels of observed and expected heterozygosities and lack of inbreeding. This pattern is possibly the consequence of an important amount of breeding occurrence abroad SWA nesting beach adjacencies, mating behaviours (such as polyandry and/or polygyny), and also some degree of inbreeding avoidance among reproductive individuals. The low remigration rates estimated for SWA subpopulation is possibly related to the high mortality rates at seas. A more comprehensive analysis on the patterns of genetic diversity, operational sex ratios, and inbreeding avoidance could help to inform about population resiliency and better understand the reproductive behaviour to perform recovery strategies and efficiently act to prevent the extinction of this isolated and remarkably threatened leatherback subpopulation from the Atlantic Ocean. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study conducted genetic assessment of the South West Atlantic subpopulation of leatherback turtles and found genetic differences and two different genetic clusters. The low number of reproductive females in the subpopulation may be due to breeding occurrence in other nesting areas, as well as mating behaviors and inbreeding avoidance. The low remigration rates estimated for the subpopulation may be related to high mortality rates at sea.