Our research focuses on the use of genetic markers and molecular tools to gain insight into the processes that shape the distribution of a variety of organisms. These genetic data are often used as a conservation tool to understand the population dynamics, ecology, evolution and biogeography of organisms that would be difficult to ascertain using traditional field technics. I am also broadly interested in cryptic species and how they can mislead management strategies. Recently, our lab has collaborated on projects with Dr. Joseph Quattro at USC Columbia on projects related to fireflies in the southeast, particularly the synchronizing firefly, Photuris frontalis.
Loggerhead Sea Turtles
Much of my research has focused on a large subadult feeding assemblage of loggerhead sea turtles (Caretta caretta) that exists off the southeastern coast of the United States from Winyah Bay, SC to St. Augustine, FL. Loggerhead sea turtle mtDNA haplotype data and serum testosterone data collected over several years were used to estimate the temporal stability of nesting beach contributions to this mixed-stock feeding aggregation. Given the relatively long maturation period in sea turtles, monitoring of subadult feeding aggregations provides a critical early warning of acute impacts to populations that might show up far earlier than in nesting beach surveys.
In addition, this unique combination of genetic and serum testosterone data in subadult sea turtles allowed for an unprecedented gender specific analysis of nesting beach contributions to subadult foraging grounds. This gender based approach to mixed-stock analyses is especially critical in sea turtles as nesting rookeries have highly variable, temperature-dependant sex ratios; not utilizing a gender based approach can mask the importance of rookeries that would be undervalued based on rookery size alone. The data indicate that the nearby nesting beaches in SC and GA, despite their population sizes being an order of magnitude smaller, contribute a disproportionately large percentage of turtles to this feeding assemblage relative to the nesting beaches that exist in central and southern Florida. The uneven nature of nesting beach gender production increases this disproportionate contribution when only one gender is considered in the mixed stock analysis; e.g., the SC and GA nesting beaches produce half of all male hatchlings in the southeastern US. In the face of a warming climate, these small northern nesting beaches will be a critical source of males for the overall population as the southern beaches become increasingly feminized.
Population Structure in Kemp’s Ridley Sea Turtles in the Gulf of Mexico
Nearly extinct in the 1980s, Kemp’s ridley sea turtles have made an impressive comeback. Despite this turnaround, they are currently the most endangered of all sea turtles, and the full impact of the Deepwater Horizon oil spill on the species remains unclear, though nearly 200 Kemp’s ridleys were known to have been killed by the acute effects of the disaster. One of the priorities of the Bi-National Recovery Plan for the Kemp’s Ridley Sea Turtle is to protect critical nesting beaches, yet conservation efforts have focused almost entirely on only two nesting populations (Rancho Nuevo, Mexico and Padre Island, TX).
The nesting population of Kemp’s ridleys at Tecolutla, Veracruz, Mexico is the largest outside of the Rancho Nuevo area with an average annual nest count of 741 nests for the years 2008-2012. Vida Milenaria (VM), a non-profit, Mexican NGO, has been patrolling approximately 42km of nesting beach at Tecolutla since 1974 and educating residents about the importance of preserving these nesting populations. Their efforts have resulted in a substantial increase in Kemp’s ridley nesting, from just a handful of nests in the 1970’s to over 800 in 2012. Although VM’s efforts have successfully protected nests from predators and poaching for many years, they have not had access to resources or expertise that would permit basic ecological studies. The increased nesting activity on Tecolutla beaches raises many important questions about the reproductive contribution of this population to the species.
Recent research suggests that certain offshore environmental conditions in the Tecolutla area promote the migration of hatchlings to their pelagic habitats; indicating that the Tecolutla nesting population may have a reproductive advantage and therefore be important to the long term survival of the species. Since the Tecolutla nesting population is geographically isolated from the Rancho Nuevo and Padre Island populations, and underwent a recent expansion, it may represent a genetically independent subunit that requires special consideration in the management efforts for the species.
I am investigating the population dynamics of Kemp’s ridley nesting beaches through genetic analyses of nesting females as well as the establishment of a long term, rigorously monitored “index nesting beach” project at Tecolutla. In addition, baseline beach and nesting data will be collected, including beach and nest temperature profiles, to help facilitate a better understanding of Tecolutla’s role in a comprehensive Kemp’s ridley management plan. Concomitantly, I have begun genetic analyses of subadult Kemp’s ridley sea turtles captured off the coast of SC, and I am partnering with IMMS and other Gulf of Mexico researchers to collect in-water samples of Kemp’s ridleys from the Gulf to assess the connectivity between subadult foraging grounds, as well as between nesting beaches and foraging grounds. These research and monitoring efforts will address high priority areas in sea turtle conservation and more specifically in the NMFS’ Kemp’s ridley recovery plan. The initial phases of this project were successfully implemented in 2014, was interrupted in 2020 due to COVID but we are planning on ramping back up again in 2026.
Invasive Species
The ecological and economic impacts of aquatic invasive species has drawn considerable attention from scientists, managers and the general public; especially in Florida, where there are many high profile invasions. From a conservation and management perspective, it is particularly valuable to understand the pathways of invasion of non-native species and the source-sink dynamics of their populations. To address these questions, I am working with researchers at the University of Florida, The Citadel and the University of Lund, Sweden, to study the invasion of a Cheloniid-specific, burrowing barnacle, Stephanolepas muricata using genetic markers. This species was considered to be endemic to the Indo-Pacific until 2011 when it was first documented in the western Atlantic. Because individuals are relatively difficult to detect, it is unclear how long S. muricata has been present in the Atlantic and how it arrived there. I have begun a global genetic study to determine possible routes of invasion into the Atlantic, as well as to determine if the barnacle exhibits host species specificity. Additionally, by comparing the population genetic structure of this species and its host, it may be possible to infer connectivity between turtle populations and, potentially, pathways of infection between turtle species with non-overlapping niches.