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Description
The hawksbill marine turtle (Eretmochelys imbricata) is a highly threatened species whose conservation status is particularly precarious in the eastern Pacific Ocean, where it is estimated that < 700 reproductively active nesting females remain. Thought to be virtually absent from this ocean region as recently as 2007, research I spearheaded since that time has led to the identification of several important nesting colonies and foraging grounds. These discoveries have improved the conservation outlook for the species, while also providing unique research opportunities. To improve understanding and management of the species, for my doctoral dissertation I implemented genetic research of hawksbills in the eastern Pacific using a combination of mitochondrial and nuclear genetic markers. Using phylogeographic analyses, I found that hawksbills colonized the eastern Pacific via the Indo-Pacific, rather than representing a relict population isolated from the Atlantic by the rising of the Panama Isthmus. Despite low genetic diversity across the region, I found strong stock structure between the principal nesting colonies, suggesting the existence of multiple populations and warranting their recognition as distinct management units. I also identified the existence of a novel “reproductive ecotype” for hawksbills nesting in mangrove estuaries that may warrant additional conservation attention. By evaluating hawksbills at foraging grounds across the region, I found that juvenile hawksbills use foraging grounds in the vicinity of their natal beaches, a pattern I termed natal foraging philopatry, which suggests that the traditional view that marine turtles home to natal areas solely for reproduction are incomplete. However, my fine-scale evaluations of genetic differentiation among foraging grounds indicated important variability at these sites, suggesting the NFP pattern manifests most clearly at regional scales. I also found discrepancies among the haplotype frequencies of several foraging grounds and rookeries, as well as the presence of several orphan haplotypes, suggesting undiscovered hawksbill rookeries likely remain in the eastern Pacific. Finally, by investigating mating systems in the hawksbill nesting colony at Bahia de Jiquilisco, El Salvador, I detected the highest levels of polygyny to date in a marine turtle population, indicating a lack of males exists for the population. I also detected multiple paternity in females, confirming polyandrous mating strategies are also employed by hawksbills at the site.
