Population genetics of green (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) in Grenada, West Indies

Abstract

Sea turtle populations within Grenada are believed to be in decline, consistent with worldwide trends. Conservation strategies for green and hawksbill turtles in Grenada are currently limited by a lack of detailed knowledge of the genetic make-up, life history and migration patterns of the local aggregates of these species. Genetic characterisation provides a means for inferring population diversity and origins for these aggregates and to assess potential impacts from regional and worldwide management strategies. Additionally, chelonid alphaherpesvirus-5 (ChHV5) and ChHV5-associated fibropapillomatosis (FP) have recently been reported within Grenada’s green turtle population, but the epidemiology of the disease in Grenada remains poorly understood. We genetically characterised Grenada’s foraging green (n = 57), nesting hawksbill (n = 18), and foraging hawksbill turtle populations (n = 22), and used mixed stock analysis (MSA) to assess the level of genetic connectivity of Grenada’s populations with other populations in the Atlantic region. Furthermore, foraging green turtles were assessed for prior exposure to ChHV5 using a serological assay to examine associations between origins and infection status. Mitochondrial DNA (mtDNA) sequencing data revealed seven haplotypes within Grenada’s foraging green turtle population, including one novel haplotype (CM-A82.1), and a total of seven haplotypes across Grenada’s nesting and foraging hawksbill turtle populations, including one (Ei-A68) and two rare haplotypes (Ei-A45, Ei-A72), respectively. We identify Grenada’s Isle de Caille rookery as a nesting population of origin for haplotype Ei-A68, which was an orphan haplotype prior to this study. MSA results indicate that Grenada’s green and hawksbill turtle populations are associated with that of 15 other countries throughout the Atlantic region. ChHV5-specific antibodies were identified in serum samples in 9.38% of green turtles, with no apparent association of ChHV5 serology status and green turtle haplotype. Mixed stock analyses strongly indicate that Grenada’s sea turtle populations are regionally shared resources and should be managed as such. Furthermore, the rare and/or unique haplotypes present within Grenada’s sea turtle populations offer valuable genetic diversity to the wider region and further conservation strategies are warranted to protect these at-risk haplotypes.