Current Research Projects
The DNA sequencing and genotyping projects largely involve using genetic markers to answer questions about wildlife ecology and behavior. This relatively new and rapidly expanding field is now commonly referred to as molecular ecology.
Dispersal, Habitat Area, and Effective Population Size of Northern Bobwhites in South Texas
David Garcia-Solorzano, Ph.D. candidate in Wildlife Science (Co-advisors: Drs. Leonard Brennan and Randy DeYoung).
The recent development of new molecular markers and molecular techniques offers a powerful new tool for studying the population biology of wildlife species. Coupled with recent advances in automated genetic analysis, these new markers provide the potential for large-scale genetic examination of wildlife populations. The objectives of my study are to use molecular genetic (DNA) tools to provide the first reliable estimates of dispersal, habitat area, and effective number of breeders for bobwhites in South Texas. By estimating dispersal, habitat area and effective population sizes for bobwhites in South Texas, I will provide a basis for understanding management and population restoration potential in other parts of Texas where available habitat is significantly more fragmented.
A Landscape-Genetic Approach to the Management of Feral Pigs in South Texas
Johanna Delgado-Acevedo, Ph.D. candidate in Wildlife Science (Co-advisors: Drs. Randy DeYoung and Tyler Campbell).
The spatial patterning, structure, and functioning of most of the ecosystems of the world have been altered by human activities. Biological invasions are an example of those activities and indeed, are one of the major threats to ecosystem function and conservation, agricultural lands, and human health. Thus, taking effective steps to prevent dispersal and establishment of invasive species constitutes an enormous challenge to scientists and resource managers. Feral pigs (Sus scrofa) are one of the most aggressive and dangerous invasive mammals due to their detrimental impacts on native wildlife species, agricultural damage, and disease risks. Taking advantage of a combination of genetic methods and GIS technologies (e.g., landscape genetics), I am seeking to improve feral pig management strategies in South Texas. Specifically, I will (1) identify geographic patterns of population structure and how landscape features affects population structure; (2) estimate dispersal rates, routes of dispersal, and determine sex-biased dispersal; and (3) to determine the origin of disease-positive individuals. The results of this study will allow the development of improved management strategies for alleviating feral pig damage in agricultural lands, reserves, and wildlife areas.
Effects of Population Density and Resource Manipulation on Breeding Success and Mating Tactics of Male White-tailed Deer
Aaron Foley, M.S. candidate (Co-advisors: Drs. Charles DeYoung, David Hewitt, Tim Fulbright, and Randy DeYoung,).
Many species of ungulates have polygynous or polygamous mating systems, where male breeding success is highly variable. The mating strategies and breeding success of males may be influenced by a variety of ecological and demographic variables, including the distribution of resources and population density. My study involves a large-scale experiment (12 200-acre enclosures), where deer density and access to resources (e.g., supplemental feed) are manipulated. I am using a panel of microsatellite DNA markers to assign parentage within each enclosure. I will use the parentage data to assess the relative importance of antler size, body size, and age on male breeding success under varying population density and resource availability.
Conservation Genetics of Reddish Egret
Elizabeth Bates, M.S. candidate (Co-advisors: Drs. Bart Ballard and Randy DeYoung).
The reddish egret (Egretta rufescens) is one of the least-studied species of heron. They inhabit coastal wetlands along the Gulf of Mexico, in the Caribbean and Bahamas, along the Atlantic coast of Florida, and along the Pacific coast of Mexico. In North America, the majority of the breeding population is located along the Texas Gulf Coast. The species is rare compared to other herons and relies completely on coastal wetlands, prompting its listing as a species of concern by the U.S. Fish and Wildlife Service and threatened by the state of Texas. Reddish egrets were nearly driven to extinction in the early 1900's by plume hunters. However, the exact impact on reddish egret numbers is unknown. Currently there are about 2,000 pairs in the United States. Numbers in Mexico and the Caribbean are unknown. Effectively managing for reddish egrets is complicated because of the limited knowledge regarding this species. Coastal development, habitat loss, and disturbance by humans are potential factors affecting reddish egret populations. The fact that this species was nearly driven to extinction suggests the possibility that the population went through a genetic bottleneck. This leads to the question of just how much genetic variability currently exists among reddish egrets. The goals of my study are to delineate geographic patterns or management units among population groups of reddish egrets and to determine the extent of genetic variability within the reddish egret populations. The results of this study should help managers to plan for the preservation of this species.
A Landscape-Genetic Approach to Assist Gray Fox Oral Rabies Vaccination Strategies in Texas
Angeline Zamorano, undergraduate research assistant (Advised by Dr. Randy DeYoung in cooperation with Dr. Jeff Root, USDA-APHIS-WS National Wildlife Research Center and Texas A&M NSF-UMEB co-mentor Dr. Rodney Honeycutt).
A distinct gray fox strain of rabies is maintained in populations of gray fox in central Texas, posing a significant health risk to other species of wildlife, to domestic animals, and to humans. To combat this health risk, a vaccine suitable for oral vaccination is dispensed in the form of oral baits, which are broadcast over the geographic area selected for rabies control. At present, the gray fox oral rabies vaccine (ORV) zone in Texas extends from the Mexican border to west-central Texas, requiring extensive effort and cost to manage (~2 million ORV baits broadcast during 2003). Conducting animal management on this massive scale clearly presents many challenges. In the case of gray fox, control efforts are hindered by a lack of knowledge regarding the ecology, movements, and dispersal of gray fox in the ORV zone. For instance, it is not known why breaks in the ORV zone (e.g., rabid animals detected outside the present vaccination area) are more likely to occur in certain geographic areas. Knowledge of terrain features that promote or inhibit dispersal among local populations would be extremely valuable for focusing rabies control efforts. To this end, the USDA-APHIS-WS National Wildlife Research Center (NWRC) is using a combination of radiotelemetry, serology, and spatial data to monitor the ORV program to increase the effectiveness of the ORV strategy. My study will add a genetic component to assess population structure and dispersal at the landscape scale.
