Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2003
Publication Date: 4/1/2004
Citation: Kim, K.S., Sappington, T.W. 2004. Boll weevil (Anthonomus grandis, Boheman) dispersal in the southern United States: Evidence from mitochondrial DNA variation. Environmental Entomology. 33:457-470. Interpretive Summary: The boll weevil is a major pest of cotton, and great efforts are underway to eradicate it from the U.S. There is concern that weevils may be flying in from neighboring areas that are still heavily infested, thus increasing the expense and time needed to eliminate this insect. Very little is known about how far weevils are likely to migrate, and new technologies are needed to identify the origin of captured weevils. In this study, we analyzed variation in the DNA of boll weevils captured from 20 different locations across eight U. S. states and northeast Mexico. Patterns of DNA variation differ depending on where the weevils were collected. From this variation, we were able to determine that migration frequently occurs between areas separated by less than 300 km (about 185 miles). The DNA of weevils captured in an eradicated or nearly-eradicated zone can be compared to the patterns of DNA variation found in our study to provide clues about the origin of the captured weevils.
Technical Abstract: An understanding of boll weevil (Anthonomus grandis, Boheman) dispersal behavior is essential to characterizing and responding to the threat of migration into eradication zones. Genetic variation in boll weevil mitochondrial DNA (mtDNA) was sampled and analyzed to make inferences on the magnitude and geographic pattern of genetic differentiation among weevil populations from 20 locations across eight U.S. states and northeast Mexico. Polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) analysis was conducted on a 12.4-kb amplicon of mtDNA from each of 419 individuals. A total of 28 distinct mtDNA haplotypes, 17 of which were unique to single locations, were identified from restriction reactions of ten informative endonucleases. Haplotype and nucleotide diversity was generally greater in southern than northern poulations, and was greater in the east than the west among nothern populations. Genetic differentiation between eastern and western populations was pronounced, and phylogenetic analyses revealed two major clades corresponding to these regions. These results are consistent with historical boll weevil range expansion into the southeastern U.S. from Mexico, and a secondary colonization of the High Plains. Evidence suggests that gene flow between eastern and western populations is limited. However, it appears that migration between locations separated by <300 km is frequent.