Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2005
Publication Date: 4/1/2005
Citation: Kim, K.S., Sappington, T.W. 2005. Genetic structuring of western corn rootworm (Coleoptera: Chrysomelidae) populations in the U.S. based on microsatellite loci analysis. Environmental Entomology. 34:494-503. Interpretive Summary: Corn rootworms are insects that attack corn, causing over $1-billion in losses each year in the U.S. They have developed resistance to crop rotation and to many insecticides, and it is feared they may become resistant to transgenic Bacillus thuringiensis ("Bt") corn as well. Thus, it is important to understand the genetics of rootworm populations. We used DNA markers called "microsatellites" to study variation in western corn rootworms across ten widely separated populations in nine U.S. states. Although there was sufficient variation in these markers to do population studies, the populations all appeared very similar genetically. We conclude that they have not had time to drift apart genetically since this insect began spreading eastward across the U.S. from the Great Plains about 50 years ago. The results of this investigation will guide scientists in the design of future studies using genetic markers to determine migration rate and population size of western corn rootworms, factors critical to successful insect resistance management.
Technical Abstract: Ten polymorphic microsatellite loci were surveyed to understand genetic structuring of western corn rootworm (Diabrotica virgifera virgifera LeConte) populations, based on 595 individuals sampled from ten locations across nine U.S. states. All populations showed high levels of genetic diversity, but little genetic differentiation. Most pairwise FST values were nonsignificant, except those involving the Texas population. There was no evidence of isolation by distance for populations from north-central Kansas to the East Coast, nor for a genetic bottleneck in any D. v. virgifera population sampled. We conclude that the D. v. virgifera populations we sampled have had insufficient time for substantial genetic structuring to develop since its recent eastward range expansion from the Great Plains beginning about 50 years ago.