Dissertation Research: Population Structure of the Green Sea Turtle Chelonia mydas

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The goal of this research is to define population structure of the endangered green sea turtle, Chelonia mydas. Green sea turtles are known to migrate extensively between shallow feeding pastures and surf-built nesting beaches. Tagging studies have demonstrated that female turtles return to the same beach to nest in successive nesting seasons. This remarkable site fidelity led researchers to suggest that female turtles return to nest on their natal beach. If green sea turtles do return to their natal beach, then each rookery should constitute an isolated breeding unit. In this study mitochondrial DNA (mtDNA) restriction analysis will be used to (1) test the natal homing hypothesis, and (2) define population structure of the green sea turtle. Samples are obtained by removing one egg per nest from 10-20 nests per rookery. Given the large number of eggs (about 100) per nest and the extremely low survival rate of eggs and hatching in nature, this sampling strategy has a negligible impact on population size. Preliminary results are consistent with the natal homing hypothesis. This proposal requests funding to complete a global survey of green sea turtle rookeries in order to genetically define major nesting assemblages. These data bear directly on questions about the reproductive behavior and dispersal of green sea turtles. Since populations are the fundamental units of species management, results are of immediate use to conservation and management agencies. In addition, it may be possible to use genetic markers generated in this study to identify the origin of green sea turtles harvested on feeding grounds in the Caribbean and elsewhere. Thus, the findings can substantially improve the data upon which international management policy must be based.