A case study of sea turtle hybridization in the north-western Caribbean verified by mitochondrial and multilocus nuclear sequences

IntroductionThe family Cheloniidae includes seven species of marine turtles, separated by tens of millions of years from their common ancestor. Despite this, there have been remarkable cases of hybridization between different species within this lineage. Herein, a case study of a specimen found near Cancun (Yucatan Peninsula, NW Caribbean, Mexico) is described.MethodsA juvenile specimen was brought to the marine turtle hospital facility at Parque Ecoarqueológico Xcaret for treatment of a severe case of fibropapillomatosis. PCR amplification and sequencing were performed to identify species parental ancestors. One mitochondrial locus (D-loop) and five nuclear loci (R35, BDNF, CMOS, RAG1, and RAG2) were analyzed on the hybrid specimen and 15 reference specimens (RS) of E. imbricata (N = 7) and C. mydas (N = 8) from different locations on the Yucatan Peninsula.ResultsThe specimen showed mixed morphological features of both Eretmochelys imbricata and Chelonia mydas. Genetic analyses showed that the hybrid specimen has a mitochondrial haplotype affiliated to C. mydas. In four nuclear loci (R35, BDNF, RAG1, and RAG2), the genotypes were heterozygous, with one allele affiliated to E. imbricata RS and the other to C. mydas RS. For the CMOS locus the results were inconsistent throughout C. mydas RS and the hybrid specimen. The results of other loci were consistent with a first-generation hybrid between a C. mydas female and E. imbricata male.ConclusionIn the Caribbean, few confirmed cases of hybridization had been reported. This record contributes to monitoring interspecific reproductive interactions of Caribbean sea turtles.