Project Title: Promiscuity in marine turtles: evolutionary push for population stability?
Project Manager: Dr. Jeanette Wyneken & Jacob Lasala
Organization: Loggerhead Marinelife Center (Non-Profit Organization)
Grant Amount: $7,773.15
Completion Date: 2019-01-21
Summary: Sex ratios, population size, and relatedness of individuals are important metrics of population status. For marine turtles, hatchling sex ratios result in a female bias at most sites. Genetic exclusion analysis (comparing maternal genotypes to offspring genotypes), allows breeding male quantities and identities to be estimated with greater accuracy; those measures then can improve estimates of operational sex ratio, as well as effective population size and illuminate breeding patterns setting baselines for Florida’s sea turtles. We compared the numbers of males and females contributing to three species of marine turtles nesting assemblages in southern Florida and determined that these turtles are promiscuous. We did not find repeating males during this study. This suggests that the number of successful males may be higher than previously expected. In species with TSD and highly female biased hatchling sex ratios, frequent multiple paternity in small nesting assemblages may signal breeding plasticity that stabilizes population sex ratios even as temperatures continue to rise. This final component of the project is important because it is necessary to know if such breeding accommodation occurs across both high and low breeding seasons. The best practice (taking advantage of advances in methods and markers) to insure this result is real across species and years is to conduct a 10% quality check of each samples year and to complete a sampling sequence for the smaller growing breeding populations (leatherbacks and greens) to fill in gaps.
Results: In 2016, we were awarded the Sea Turtle Grant 16-035R, which allowed us to sample from repeating loggerhead nesters and increase our sample size of leatherbacks and green sea turtles. The current grant helped us to complete analysis on some of these samples and start the process to publish our findings. The first paper to address our findings was published in PLoS One this past February (link at end) where we identified the breeding sex ratio of loggerheads nesting in Sanibel (~2.5 males per female). We are in the process of finalizing another manuscript for the repeating loggerhead nests collected in 2016. In 2017, Jake limited his collection of samples to leatherbacks and green sea turtles in Boca Raton and Juno Beach. From 2013-2016, the research covered three beaches across the state and not all the sampling goals were met equally. Jake identified that for both species the two nesting populations were genetically the same population, so we felt confident in focusing our sampling. Throughout the season, he sampled from a total of 2,104 turtles (2,107 hatchlings and 87 adults). This grant allowed us to extract DNA from every individual and then genotype them for publication. To date all the samples from 2017 have been analyzed and we are currently in the process of writing two manuscripts for submission.