Research in Bill Walton's Laboratory

 

 

 

 

 

 

 


Research and Publications:  I am an aquatic entomologist and ecologist who works mostly in natural and man-made wetlands.  Currently, the research in my laboratory has two foci: wetlands ecology with an emphasis on mosquitoes and bacteria used as an environmentally friendly method for controlling mosquitoes.  Links to recent publications can be found either in the links in the paragraphs below or in the list of publications link at the bottom of this section of the web page.

  

The major emphasis of the wetlands research in my laboratory group is to integrate studies of mosquito biology and ecology with the design of control methodologies for pestiferous and pathogen-transmitting mosquitoes in wetlands.  We have been studying the effects of design features and management strategies for multipurpose constructed treatment wetlands on mosquito production and water quality performance.  In addition to studying the relationship of nutrients and other water quality variables to mosquito populations, our studies have focused across the food web from the temporal and spatial dynamics of bacterial populations to studies on alternative larvivorous fishes to the mosquitofish (Gambusia affinis) and collaborative studies with USGS scientists on the relationship of aquatic insect production to bird usage of wetland habitats.  Our applied research on mosquito control in man-made wetlands has been complemented with basic research on the population dynamics of larval mosquito populations, the ecological stoichiometry of mosquitoes, the interaction of mosquitoes with natural enemies, and the influence of vegetation on the temporal and spatial distribution of mosquito larvae in wetlands.

 

A second research emphasis in my laboratory is the evolution of resistance to bacterial larvicides and the ecological consequences of evolved resistance.  Bacterial larvicides are perhaps the most promising method of environmentally friendly mosquito control currently available, particularly in treatment wetlands.  Two Bacillus are currently used for mosquito control in California; Bacillus sphaericus is comparatively more effective than is Bacillus thuringiensis subsp. israelensis (Bti) against mosquitoes inhabiting the organically enriched waters of most treatment wetlands.  Unlike Bti which contains multiple toxins that limit the potential for the rapid evolution of resistance in mosquitoes, the two toxin precursors in B. sphaericus act as a single toxin following ingestion and partial digestion by mosquito larvae.  Mosquitoes can evolve resistance to the B. sphaericus toxin very rapidly (>10,000-fold in 7-8 generations).  This finding takes on added significance for mosquito control in treatment wetlands of southern California because our studies of mosquito dispersal demonstrated that there is little potential gene exchange among populations of the predominant mosquito occurring at thickly vegetated wetlands.  Consequently, there is a greatly reduced potential for a resistant population to exchange genes with a nearby population that is susceptible to B. sphaericus.

 

We have been collaborating with Dr. Brian Federici and his laboratory on an NIH-funded project studying the development, modes of action and spectra of resistance/cross-resistance of transgenic strains of Bacillus that have been engineered for both increased efficacy against mosquitoes and a reduced potential for the evolution of resistance in the target mosquito populations.  Dr. Margaret Wirth coordinates this work in my laboratory and, in addition to her considerable expertise in studies of insect resistance, oversees the maintenance of 22 colonies of mosquitoes that have been selected for resistance to various Bacillus toxins and insecticides.  We also have collaborated recently on related projects with colleagues at the Pasteur Institute in Paris, Ohio State University, Cardiff University and Ben-Gurion University of the Negev.  The findings of these studies have important implications for genetic engineering of bacterial larvicides and resistance management in programs using bacterial larvicides as an environmentally-friendly approach to mosquito control.

 

A recent focus of work in my laboratory was on the factors causing morphological abnormalities in wood frogs on the Kenai National Wildlife Refuge.  Peter Jensen (formerly a student in John Trumble's lab) and I were working as part of a multi-disciplinary group of scientists on this project that was coordinated by the Environmental Contaminants Branch of the U.S. Fish and Wildlife Service (USFWS) in Anchorage.  The incidence of abnormalities in recently metamorphic frogs from wetlands and ponds on the Kenai NWR (annual average for 2000 to 2003: 6-10% of metamorphs; incidence of abnormalities as high as 19% for particular ponds) is among the highest observed for Alaskan wildlife refuges.  The goals of the project were to identify the factors contributing to the high incidence of abnormalities in metamorph wood frogs and to help update management policies for the Kenai NWR.  Our role in this project was to assess the relative contribution of predacious aquatic insects for causing limb abnormalities in wood frogs across a gradient of potential human-use impacts on aquatic habitats on the refuge.

 

List of publications

 

Recent Teaching:

 

Biology 005C, Introductory Evolution and Ecology
Biology 265, Advances in Population and Evolutionary Biology
Entomology 114, Aquatic Insects

Entomology 127, Insect Ecology
Entomology 255, Seminar in Medical and Veterinary Entomology

Entomology 276, Research Seminar in Medical, Urban and Veterinary Entomology

 

 

 

 

 

Current Staff:

       Peggy Wirth, Ph.D.

          David Popko, M.S.

Peter Brabant, B.S.

 

Current Students:

       Donald Beasley (Entomology), M.S. candidate

          Dagne Duguma (Entomology), Ph.D. candidate

          Jennifer Henke (Entomology), Ph.D. candidate

          Adena Why (Entomology), M.S. candidate

         

Undergraduate Students:

          Henrique Chan

          Christina Handayan

Navit Mujica

          Bich Nguyen

          Justin Richardson

         

         

Prospective Graduate Students:

I am most interested in working with students who have a strong interest in the study of aquatic insect ecology or vector ecology.  Besides serving on committees of graduate students enrolled in the Entomology Graduate Program, I have recently served on the qualifying exam, thesis or dissertation committees of students in the departments of Biology and Environmental Sciences.  I can sponsor graduate students in the Evolution, Ecology and Organismal Biology Graduate Program as part of the Evolution and Ecology Graduate Research Unit.  I am also associated with the Center for Conservation Biology and recently served as the advisor to undergraduates in the Conservation Biology track in the interdepartmental Biological Sciences Program. Prospective students are welcome to contact me before applying to best determine which program is most appropriate for their interests and prior training.

Pictures of some lab-related goings-on