Genetic variation, mating patterns and reproductive dynamics in American alligators.

摘要

The aim of this study is to examine several aspects of American alligator population biology. First, the overall genetic variation inherent in alligators from twelve localities throughout the southeastern United States is evaluated to answer questions about gene flow and population sub-division. Analyses using eight polymorphic microsatellite loci support the hypothesis of an east-west phylogeographic split in American alligator populations. Florida and south Georgia samples form a randomly mating population distinct from several Louisiana and Texas localities which form a separate, panmictic group. Samples collected from Mobile, Alabama and Santee Coastal Reserve, South Carolina are significantly different from either of these groups as well as from each other. These results are consistent with studies of many freshwater fish and aquatic and terrestrial turtles distributed throughout this same geographic region.; Further investigations of alligators from Rockefeller Wildlife Refuge, Louisiana and the Savannah River Site, South Carolina provide new insight into the fine-scale mating patterns and reproductive dynamics in these localities. For example, many female American alligators produce multiply-sired broods with skewed paternity. Females also produce nests in the same general area among years (nest area fidelity), though not necessarily with the same male(s) (mate fidelity). Large males are successful in siring multiple clutches both within and among years in the same general area. Many of these findings are consistent with observed mating behaviors in captive and wild alligators and provide a link between the behavioral and genetic mating systems in this species.; Analyses of mutation rates were performed among Savannah River Site and Santee Coastal Reserve, SC and Rockefeller Wildlife Refuge, LA populations. As the Savannah River Site contains low level radioactive and heavy metal contamination, it was hypothesized that this site would have significantly higher microsatellite mutation rates than either of the other two “clean” sites. However, preliminary data suggests that the Savannah River Site mutation rate is not significantly higher than either the Santee Coastal Reserve or the Rockefeller Wildlife Refuge.; Lastly, this work considers how one prominent hypothesis, the differential allocation hypothesis, could be applied to mating systems in crocodilians and in other reptilian species.