Molecular ecology of hawksbill turtles Eretmochelys imbricata in the Seychelles
Molecular genetics are an invaluable tool in whole-organism biology, allowing the indirect investigation of life history traits and evolutionary processes that are otherwise unobservable. In this thesis, I apply molecular genetic techniques to the study of the hawksbill sea turtle Eretmochelys imbricata, using a population in the Republic of Seychelles. My aim in this study was two-fold. Firstly, to better characterise certain key aspects of the hawksbill’s life history and demography, with a view to better informing hawksbill conservation. Secondly, to test several hypotheses relating to broader evolutionary questions, e.g. regarding the forces shaping mating systems and the link between individual genetic variability and fitness. I found that the majority of females were fertilised by a single male each, and that they used stored sperm to fertilise all of their multiple clutches across a nesting season. There was no evidence of females biasing paternity towards males with particular genetic properties (variability, dissimilarity), suggesting that females are not using sperm storage to promote sexual selection. Males were rarely seen to fertilise more than one female in the study, suggesting low reproductive skew and a large male population that is mobile and/or dispersed. Females at nesting beaches spanning 450 km comprised a single genetic stock, but males were more dispersive than females. I found that the effective size of the population was relatively large, and did not show signs of inbreeding or loss of genetic variation following the substantial reduction in hawksbill numbers caused by historic overhunting. Finally, I found that both male genetic variability and parental genetic dissimilarity can predict nest success, but in a way that might select for a stabilised level of genetic variability. I discuss the implications of these results for both evolutionary biology and the ongoing conservation management of a species internationally listed as critically endangered.
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