The lab studies a variety of questions related to the population genetics and evolution of herbivorous insects, especially crop pests. Major areas of interest include:
Of course, understanding these evolutionary processes has practical impacts on our ability to limit the harm that pest insects can do. However, crop pests can also serve as good model systems for more general evolutionary questions. For example, understanding how crop pests adapt to changes in pest management or other farming practices can help us to understand how organisms in general adapt to sudden and widespread changes in their environment.
The rapid and widespread introduction of crops that have been genetically-modified to resist insects can be thought of as an example of sudden, dramatic environmental change. In some cases, insect pests have displayed a remarkable ability to adapt to GM crops. The western corn rootworm was able to adapt to rootworm-resistant GM corn in as little as six generations. What’s more, resistant populations of western corn rootworms appeared almost simultaneously throughout much of the US Corn Belt. This raises the question, did different populations arrive at the same adaptations independently, or are there many ways to become resistant to GM corn? To answer this question, we are working to identify the genes responsible for resistance to GM corn from populations of western corn rootworms in several US states.
Caterpillars of the western bean cutworm, Striacosta albicosta, feed on corn and dry bean plants. Oddly, they are not generalist feeders that eat a wide range of plants but appear to specialize on just corn and beans. We are trying to find out if western bean cutworms developing on corn and those developing on beans represent a single population or are structured into host-associated populations. Answering this question will help us to understand the basic biology of this unusual feeding behavior and may also be important to managing the evolution of resistance to pesticides.
Specializing on a single niche gives organisms the opportunity to evolve adaptations to optimally exploit that niche. Being flexible enough to exploit multiple niches is a good bet-hedging strategy against the loss of a single niche. During the evolution of herbivorous insects, there have been many transitions between specialist feeding on a narrow range of plants and generalist feeding on a wide variety of plants. We are using the beetle genus Diabrotica as a model system to study the basis of specialist versus generalist feeding. The genus allows us to make comparative studies of congeneric species with similar life histories, physiology and behavior, but very different food plant ranges. For example larvae of Diabrotica virgifera virgifera are only able to survive on corn and a handful of other grass species. In contrast, Diabrotica undecimpunctata larvae can survive on a diverse range of food plants including corn, squash and peanuts.