Extensive hybridization in hawksbill turtles (Eretmochelys imbricata) nesting in Brazil revealed by mtDNA analyses

Abstract

Bahia state hosts over 90% of hawksbill (Eretmochelys imbricata) nests registered in the main nesting sites monitored by Projeto Tamar-IBAMA in Brazil. The genetic diversity of this hawksbill population (n=119) was assayed through the analyses of 752 bp of the mitochondrial DNA control region in nesting females. Seven distinct haplotypes, defined by 125 polymorphic sites, were found. Most of the individuals (n=67) display four typical hawksbill haplotypes, 50 individuals display two haplotypes characteristic of the loggerhead turtle (Caretta caretta) and two individuals had a haplotype affiliated with the olive ridley (Lepidochelys olivacea). These results demonstrate hybridization between the hawksbills and two species that nest along the Bahia coast. Of special interest is the high occurrence of loggerhead  hawksbill hybrids (42%), which display loggerhead mtDNA haplotypes but are characterized morphologically as hawksbills. The true hawksbill haplotypes present only three variable sites and low genetic diversity values (h=0.358±0.069; p=0.0005±0.0001). The occurrence of several nesting individuals with identical mtDNA from another species may also suggest a long history of introgression between species producing likely F2 or further generation hybrids. Marine turtle hybrids have been previously reported, but the high frequency observed in Bahia is unprecedented. Such introgression may influence evolutionary pathways for all three species, or may introduce novel morphotypes that develop apart from the parental species. The presence of a unique hybrid swarm has profound conservation implications and will significantly influence the development and implementation of appropriate management strategies for these species.

First report of an olive ridley (Lepidochelys olivacea) inside the Mediterranean Sea

“…This haplotype differs in one single transition from the other Atlantic haplotype (E), and in another transition from Indo-Pacific haplotype J (Bowen et al, 1998;Shanker et al, 2004). The sequence also matched the 627-bp fragment found in 10 individuals from the same Brazilian population (Lara-Ruiz et al, 2006) in several loggerhead (Caretta caretta) and hawksbill (Eretmochelys imbricata) turtles from the same site that had a Lepidochelys olivacea mtDNA introgression (Genbank accession numbers: EU365972.1 for the wild L. olivacea haplotype and EU365971.1 for the C. caretta introgressed haplotype; Reis et al, 2010). The full sequence did not match any of the available ~800-bp sequences for the species as no recent study that used the same set of markers included any individual from the populations of Brazil, Suriname or Guinea Bissau.…”

Seleção de locais de nidificação e sucesso de eclosão da tartaruga-de-pente e da tartaruga-cabeçuda (Testudines, Cheloniidae) na Praia de Arembepe, nordeste do Brasil

“…Lara-Ruiz et al (2006) detected a frequency of 42% of the hawksbill females sampled in the region as hybrids of this two species. Behavioral comparisons between pure and hybrid hawksbills have not yet been undertaken but if there is a genetic aspect to determination of nesting behavior, it is possible that there are differences between pure and hybrid individuals.…”

mtDNA variation of the critically endangered hawksbill turtle (Eretmochelys imbricata) nesting on Iranian islands of the Persian Gulf

“…Clade A belonged to haplotypes Iran1, 2, 4, 5, 6, and to haplotypes from the Indo-Pacific Ocean, Ei2, 3, 8. Clade 2 belonged to haplotypes EiA11, EiA20, EiA45 (Velez-Zuazo et al, 2008) and BR9 (Lara-Ruiz et al, 2006) from the Atlantic Ocean.…”