Current projects in the Vargo Lab
We use molecular genetic tools, primarily microsatellite markers and mtDNA sequence data, to conduct basic and applied studies of termites and other insect pests of human structures. Our work on termites encompasses the breeding structure of colonies, colony and population genetic structure, invasion biology, foraging areas, colony densities and population dynamics. Research on other structural pests, mainly ants, cockroaches and bedbugs, focuses on population genetic structure, invasion biology, and dispersal.
The cryptic underground foraging habits of subterranean termites have hampered understanding of their foraging ranges, colony densities and colony-colony interactions. We use microsatellite markers to “fingerprint” individuals belonging to different colonies and to delineate colony foraging areas. Our results show that while colony foraging areas vary considerably among species and sometimes among different populations of the same species, they are generally rather small not exceeding a few dozen square meters. Exceptions to this rule are colonies of Reticulitermes virginicus and Coptotermes formosanus, which can forage 100+ linear meters. We’ve also conducted studies around residential properties in North Carolina and found colony densities were quite high averaging about 62 colonies per hectare (25 per acre) (Parman and Vargo 2008), as well as tracked colonies over time after treatment with baits and non-repellent liquid termiticides.
Invasive species pose major economic and ecological problems worldwide. Social insects are among the most damaging invasive species. The particular attributes that make some species successful invaders is a major area of study in invasion biology. We are conducting comparative studies of colony breeding structure and population genetic structure in native and introduced populations of invasive termites to determine if invasion success is related to changes in social organization and genetic diversity as found in some invasive ants. We are also conducting phylogeographic studies to determine possible source populations and routes of introduction of invasive termites. We are focusing on two species: 1.) the Formosan subterranean termite, Coptotermes formosanus, a native of China that has become established in many places around the world including Hawaii and the U.S. mainland; and 2.) the eastern subterranean termite, Reticulitermes flavipes, a native of the eastern U.S. that has been introduced to France and Chile.
The German cockroach, Blattella germanica, is a major pest in human structures worldwide, and its presence is a major health concern, especially for asthma sufferers. We are studying the population genetic structure of this species at spatial scales ranging from the very local - among aggregations located in the same room to global – among cities on different continents. Results of these studies will shed important new light on the dispersal abilities of German cockroach infestations and on routes of infestation on a global scale. This species has emerged as a major pest in swine production facilities in North Carolina and elsewhere. We are studying the relationships of cockroach populations among different farms using common feed and supply routes. Information generated by these studies should be helpful in designing more effective control strategies for B. germanica in both the urban and agricultural environments.
The bed bug, Cimex lectularius, has undergone a recent resurgence worldwide, including the U.S. where it is now commonly found in apartments, homes, hotels, and poultry farms. The reasons for this global outbreak are not known, but several hypotheses have been proposed, including the development of resistance and spread of resistant populations from local or global sources. We are using microsatellites and mtDNA markers to investigate population genetic structure and gene flow at different spatial scales ranging from the global to the individual apartment building. Our objectives are to shed light on the sources of bed bug infestations, the dispersal of bed bugs within and between the urban and agricultural environments, and the potential for resistance genes to spread.