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.

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Colony breeding structure in subterranean termites

Photo by Kenji Matsuura - 2009An important area of social insect biology concerns the causes and consequences of colony breeding structure, i.e., the number of reproductives heading colonies and the degree of relatedness among them. Termite colonies have a complicated life history, starting as simple families headed by monogamous pairs of reproductives (king and queen) that can later be replaced by secondary reproductives who inbreed within the colony to form extended families. In addition, colonies can sometimes be mixed families headed multiple unrelated reproductives. We use highly variable molecular markers, primarily microsatellites, to determine colony breeding structure and levels of inbreeding in subterranean termites. Our goal is to determine the role of ecological factors in shaping termite breeding systems. We are currently studying species of Reticulitermes and Coptotermes in the U.S., Europe, China and Japan.

Collaborators: Anne-Geneviève Bagnères (University of Tours, France), Claudia Husseneder (Louisiana State University), Kenji Matsuura (Okayama University, Japan) and Mo Jianchu (Zhejiang University, China).

Representative publications

  • Vargo, E. L., P. E. Labadie and K. Matsuura. 2011. Asexual queens succession in the subterranean termite Reticulitermes virginicus. Proceedings of the Royal Society of London, B. Published online 10 August 2011.
  • Matsuura, K., E. L. Vargo, K. Kawatsu, P. E. Labadie, H. Nakano, T. Yashiro and K. Tsuji. 2009. Queen succession through asexual reproduction in termites. Science 323:1687.
  • Vargo, E. L. and C. Husseneder. 2009. The biology of subterranean termites: Insights from molecular studies on Reticulitermes and Coptotermes. Annual Review of Entomology 54: 379-403.
  • DeHeer, C. J. and E. L. Vargo. 2006. An indirect test of inbreeding depression in the termites Reticulitermes flavipes and R. virginicus. Behavioral Ecology and Sociobiology 59: 753-761.
  • DeHeer, C. J., M. Kutnik, E. L. Vargo and A. –G. Bagnères. 2005. The breeding system and population structure of the termite Reticulitermes grassei in southern France. Heredity 95: 408-415.
  • Vargo, E. L. 2003. Hierarchical analysis of colony and population genetic structure of the eastern subterranean termite, Reticulitermes flavipes, using two classes of molecular markers. Evolution 57: 2805-2818.
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Colony foraging areas, colony densities, and population dynamics of subterranean termites

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.

Collaborators: Anne-Geneviève Bagnères (University of Tours) and Claudia Husseneder (Louisiana State University).

Representative publications
  • Parman, V. and E. L. Vargo. 2010. Colony level effects of imidacloprid in subterranean termites (Isoptera: Rhinotermitidae). Journal of Economic Entomology 103: 791-798.
  • Parman, V. and E. L. Vargo. 2008. Population density, species abundance and breeding structure of subterranean termite colonies in and around infested houses in central North Carolina. Journal of Economic Entomology 101: 1349-1359.
  • Vargo, E. L., T. R. Juba and C. J. DeHeer. 2006. Relative abundance and comparative colony breeding structure in subterranean termites (Reticulitermes flavipes, R. virginicus, R. hageni, and Coptotermes formosanus) in a South Carolina lowcountry site as revealed with molecular markers. Annals of the Entomological Society of America 99: 1101-1109.
  • DeHeer, C. J. and E. L. Vargo. 2004. Colony genetic organization and colony fusion in the termite Reticulitermes flavipes as revealed by foraging patterns over time and space. Molecular Ecology 13: 431-441.
  • Vargo, E. L. 2003. Genetic structure of Reticulitermes flavipes and R. virginicus (Isoptera: Rhinotermitidae) colonies in an urban habitat and tracking of colonies following treatment with hexaflumuron bait. Environmental Entomology 32: 1271-1282.
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Invasion biology of subterranean termites

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.

Collaborators: Anne-Geneviève Bagnères (University of Tours, France), Claudia Husseneder (Louisiana State University), Ken Grace (University of Hawaii) and Mo Jianchu (Zhejiang University, China).

Representative publications
  • Husseneder, C., D. Simms, J. R. Delatte, C. Wang, J. K. Grace and E. L. Vargo. 2011. Genetic diversity and colony breeding structure in native and introduced populations of the Formosan subterranean termite, Coptotermes formosanusBiological Invasions. Online First.
  • Husseneder, C., J. E. Powell, J. K. Grace, E. L. Vargo and K. Matsuura. 2008. Worker size in the Formosan subterranean termite in relation to colony breeding structure as inferred from molecular markers. Environmental Entomology 37: 400-408.
  • Vargo, E. L., C. Husseneder, D. Woodson, M. G. Waldvogel and J. K. Grace. 2006. Genetic analysis of colony and population structure of three introduced populations of the Formosan subterranean termite (Isoptera: Rhinotermitidae) in the continental United States. Environmental Entomology 35: 151-166.
  • Dronnet, S., M. Chapuisat, E. L. Vargo, C. Lohou and A. –G. Bagnères. 2005. Genetic analysis of the breeding system of an invasive subterranean termite, Reticulitermes santonensis, in urban and natural habitats. Molecular Ecology 14: 1311-1320.
  • Vargo, E. L., C. Husseneder and J. K. Grace. 2003. Colony and population genetic structure of the Formosan subterranean termite, Coptotermes formosanus, in Japan. Molecular Ecology 12: 2599-2608.
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Population genetics of German cockroaches in urban and

agricultural environments

sThe 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.

Collaborators: Coby Schal (NCSU).

Representative publications

  • Booth, W., R. G. Santangelo, E. L. Vargo, D. V. Mukha and C. Schal. 2011. Determination of population genetic structure in German cockroaches (Blattella germanica): Differentiated islands in an agricultural landscape. Journal of Heredity 102: 175-183.
  • Crissman, J. R., W. Booth, R. G. Santangelo, D. V. Mukha, E. L. Vargo and C. Schal. 2010. Population genetic structure of the German cockroach (Blattodea: Blattellidae) in apartment buildings. Journal of Medical Entomology 74: 553-564.
  • Booth, W., S. M. Bogdanowicz, P. A. Prodöhl, R. G. Harrison, C. Schal and E. L. Vargo. 2007. Identification and characterization of 10 polymorphic microsatellite loci in the German cockroach, Blattella germanica. Molecular Ecology Notes 7: 648-650.
  • Mukha, D., V., A. S. Kagramanova, I. V. Lazebnaya, O. E. Lazebnyi, E. L. Vargo and C. Schal. 2007. Intraspecific variation and population structure of the German cockroach, Blattella germanica, revealed with RFLP analysis of the nontranscribed spacer region of ribosomal DNA. Medical and Veterinary Entomology 21: 132-140.
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Phylogeographic and population genetic analysis of the common

bed bug

sThe 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.

Collaborators: Coby Schal (NCSU)

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Microsatellite development

Representative publications

  • Booth, W., E. Youngsteadt, C. Schal and E. L. Vargo. 2009. Characterization of 8 polymorphic microsatellite loci in the Neotropical ant-garden ant, Camponotus femoratus (Fabricius). Conservation Genetics 10: 1401-1403.
  • Booth, W., E. Youngsteadt, C. Schal and E. L. Vargo. 2009. Polymorphic microsatellite loci for the ant-garden ant, Crematogaster levior (Forel). Conservation Genetics 10: 639-641.
  • Booth, W., V. R. Lewis, R. L. Taylor, C. Schal and E. L. Vargo. 2008. Identification and characterization of 15 polymorphic microsatellite loci in the western dry-wood termite, Incisitermes minor (Hagen). Molecular Ecology Resources 8: 1102-1104.
  • Booth, W., S. M. Bogdanowicz, P. A. Prodöhl, R. G. Harrison, C. Schal and E. L. Vargo. 2007. Identification and characterization of 10 polymorphic microsatellite loci in the German cockroach, Blattella germanicaMolecular Ecology Notes 7: 648-650.
  • Dronnet, S., A. -G. Bagnères, T. R. Juba and E. L. Vargo. 2004. Polymorphic microsatellite loci in the European subterranean termite, Reticulitermes santonensis Feytaud. Molecular Ecology Notes 4: 127-129.
  • Vargo, E. L. and G. Henderson. 2000. Identification of polymorphic microsatellite loci in the Formosan subterranean termite Coptotermes formosanus Shiraki. Molecular Ecology 9: 1935-1938. 
  • Vargo, E. L. 2000. Polymorphism at trinucleotide microsatellite loci in the subterranean termite Reticulitermes flavipes. Molecular Ecology 9: 817-820.