Recent Demographic History and Present Fine-Scale Structure in the Northwest Atlantic Leatherback (Dermochelys coriacea) Turtle Population

Abstract

The leatherback turtle Dermochelys coriacea is the most widely distributed sea turtle species in the world. It exhibits complex life traits: female homing and migration, migrations of juveniles and males that remain poorly known, and a strong climatic influence on resources, breeding success and sex-ratio. It is consequently challenging to understand population dynamics. Leatherbacks are critically endangered, yet the group from the Northwest Atlantic is currently considered to be under lower risk than other populations while hosting some of the largest rookeries. Here, we investigated the genetic diversity and the demographic history of contrasted rookeries from this group, namely two large nesting populations in French Guiana, and a smaller one in the French West Indies. We used 10 microsatellite loci, of which four are newly isolated, and mitochondrial DNA sequences of the control region and cytochrome b. Both mitochondrial and nuclear markers revealed that the Northwest Atlantic stock of leatherbacks derives from a single ancestral origin, but show current genetic structuration at the scale of nesting sites, with the maintenance of migrants amongst rookeries. Low nuclear genetic diversities are related to founder effects that followed consequent bottlenecks during the late Pleistocene/Holocene. Most probably in response to climatic oscillations, with a possible influence of early human hunting, female effective population sizes collapsed from 2 million to 200. Evidence of founder effects and high numbers of migrants make it possible to reconsider the population dynamics of the species, formerly considered as a metapopulation model: we propose a more relaxed island model, which we expect to be a key element in the currently observed recovering of populations. Although these Northwest Atlantic rookeries should be considered as a single evolutionary unit, we stress that local conservation efforts remain necessary since each nesting site hosts part of the genetic diversity and species history.

Admixture and the organization of genetic diversity in a butterfly species complex revealed through common and rare genetic variants

“…; Molfetti et al . ). The average age of rare variants could have other effects on their geographic distribution.…”

Contextualising the Last Survivors: Population Structure of Marine Turtles in the Dominican Republic

“…The Dominican Republic nesting population from the present study was similar to the other Caribbean nesting populations forming part of a third MU in the region. The use of 711 bp sequences did not change the number of haplotypes in the Dominican Republic in contrast to previous studies, where some 496 bp haplotypes were subdivided into multiple 711 bp haplotypes [62]–[63]. Future work expanding the use of 711 bp sequences to other nesting and feeding areas is needed in order to test if longer sequences improve resolution of population structuring as they have for the loggerhead turtle [44].…”

“…Sequences were aligned by eye using the program BioEdit 5.0.9 [60] and compared with the short (<500 bp ) haplotypes previously described for the leatherback turtle [61]–[63] and the hawksbill turtle [35], [38], [40], [64]–[67]. Additionally, the whole fragment was compared to known long (>500 bp ) haplotypes described in those manuscripts that used the same or similar primers in the leatherback turtle [62]–[63] and the hawksbill turtle [35], [40]–[42], [67].…”

“…Additionally, the whole fragment was compared to known long (>500 bp ) haplotypes described in those manuscripts that used the same or similar primers in the leatherback turtle [62]–[63] and the hawksbill turtle [35], [40]–[42], [67]. Green turtle sequences were compared with the haplotypes found in the database maintained by the Archie Carr Center for Sea Turtle Research (http://accstr.ufl.edu/) that includes all published haplotypes.…”

Phylogeography, genetic stocks, and conservation implications for an Australian endemic marine turtle

“…For marine turtles, this has been a requisite for their evolutionary survival, notwithstanding the extinction of several species in the past (Cadena & Parham, ). Levels of nDNA diversity in flatback turtles were similar across rookeries, and there was no evidence of inbreeding, but diversity was lower than that observed in most other marine turtles, including green (Bradshaw et al, ; FitzSimmons, Moritz, et al, ), Kemp's ridley (Frey, Dutton, Shaver, Walker, & Rubio, ), leatherback (Molfetti et al, ), and loggerhead turtles (Monzón‐Argüello et al, ). Although, theoretically, this could indicate a reduced ability to adapt, not all of the observed reduction in genetic diversity in flatback turtles can be attributed to their biology or population history, and the loci used may not reflect levels of functional diversity within gene coding regions.…”