Genetic Diversity and Natal Origins of Green Turtles (Chelonia mydas) in the Western Gulf of Mexico
Chelonia mydas (Green Turtle) foraging areas, where juveniles, subadults, and adults of diverse natal origins coalesce and spend a large portion of their lives, can be located thousands of kilometers from nesting beaches. Unfortunately, the natal origin of turtles in many foraging areas remains unknown. Resolution of this issue was recently listed among the conservation priorities for the species by a global panel of Green Turtle researchers. We examined the genetic diversity and natal origins of Green Turtles from a well-known foraging area in the western Gulf of Mexico. Bayesian mixed-stock analysis of mitochondrial DNA haplotypes was used to demonstrate that an overwhelming percentage (∼95%) of individuals in the western Gulf of Mexico foraging group likely originate in other Gulf of Mexico and northern Caribbean rookeries, with smaller contributions from the western and southern Caribbean, and potentially the Mediterranean Sea. Management of Green Turtles in the western Gulf of Mexico will be improved by linking conservation efforts aimed at this foraging group to turtle aggregates occurring in other critical habitats within the recently defined northwest Atlantic Green Turtle regional management unit.Abstract
Map of the major rookery groups sampled previously and used for stock contribution estimates to the western Gulf of Mexico foraging group. Samples combined for mixed-stock analysis are indicated by dashed ovals (the south Atlantic group, not shown, was also a combination of multiple rookery samples). Exact sampling locations of the Texas foraging group are indicated in the map inset as EMB (East Matagorda Bay), SAB (San Antonio Bay), NPI (North Padre Island), and SPI (South Padre Island).
Age structure of cold-stunned and stranded Green Turtles in south Texas estimated from straight carapace length using the von Bertalanffy growth equation parameters of Bjorndal et al. (1995). Age distribution is broken down by site (NPI = North Padre Island, SPI = South Padre Island). Turtles from small samples (East Matagorda Bay and San Antonio Bay) were not given age estimates.
Estimated stock contribution of six regional nesting stocks to the western Gulf of Mexico Green Turtle foraging group, broken down by (A) Atlantic regional rookery groups, and (B) single Gulf of Mexico rookeries. The bars above and below point estimates represent the two-tailed 95% confidence interval around stock estimates.
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