Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2003
Publication Date: 11/1/2003
Citation: ROEHRDANZ, R.L., SZALANSKI, A.L., LEVINE, E. MITOCHONDRIAL DNA AND ITS1 DIFFERENTIATION IN GEOGRAPHICAL POPULATIONS OF NORTHERN CORN ROOTWORM, DIABROTICA BARBERI (COLEOPTERA: CHRYSOMELIDAE): IDENTIFICATION OF DISTINCT GENETIC POPULATIONS. ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA. 2003. v. 96(6). p. 901-913. Interpretive Summary: We have examined the genetic variation of mitochondrial DNA (mtDNA) and nuclear ribosomal DNA in local and dispersed geographical populations of northern corn rootworms. The goals include the survey population diversity and to determine if molecular marker systems can be used for identifying strains and emerging phenotypes that might affect area wide control programs. We have found molecular genetic evidence for two distinct populations of northern corn rootworm. A sharp boundary between the two populations in eastern Illinois separates an eastern from a western group. The populations have little genetic mixing. Although the molecular genetic differences we describe have not been specifically correlated with any behavioral differences they do raise a caution flag. Researchers in both the eastern and western regions need to be alert to the possibility that quantitative or qualitative phenotypic differences may exist between the two populations of northern corn rootworm that could cause them to react differently to control measures.
Technical Abstract: Genetic variation of mitochondrial DNA (mtDNA) and the nuclear ribosomal spacer, ITS1, in local and dispersed geographical populations of northern corn rootworm, Diabrotica barberi Smith and Lawrence was examined. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for mtDNA and DNA sequencing plus PCR-RFLP analysis was used for ITS1. Insects were collected from 66 locations in 10 states ranging from PA to KS and ND. Sequencing of the 645-646 bp ITS1 amplicon from 19 individual beetles revealed two polymorphic sites, one of which altered a restriction site for the restriction enzyme Bcl I. PCR-RFLP analysis of insects from 38 sample sites with Bcl I detected three genotypes. Many beetles had heterogeneity at the nucleotide site recognized by Bcl I, which was supported by DNA sequence data. Populations east of IL were homogeneous for one genotype, two genotypes were observed in IL, WI and ND, while SD, NE, IA, and KS populations were composed of all three genotypes. There appears to be a phylogeographic pattern of ITS1 genetic diversity. The mtDNA had 58 haplotypes that displayed a strong east-west geographical partition. The region of overlap occurred in a few counties of east-central IL. Populations to the east had less variability (9 haplotypes) than those to the west (46 haplotypes). The remaining haplotypes were recovered only in the boundary zone. Trees based on genetic distance measurements of the mtDNA produced two distinct clades. One clade contained all the eastern haplotypes along with a group of haplotypes from the northern Great Plains. The other clade included the remaining western haplotypes. Possible reasons for this population structure including expansion from different glacial relicts, historic host plant differences, and endosymbiont driven reproductive incompatibilities are discussed. Observed genetic demarcation is relevant given regional differences in the occurrence of multi-year diapause and the impending release of Bt genetically modified corn developed for the control of corn rootworms.