Submitted to: National Entomological Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/27/2001
Publication Date: 12/8/2001
Technical Abstract: Long-PCR-RFLP was used to examine the geographical variability of northern corn rootworm (D. barberi), NCR. 59 haplotypes were observed among 603 individuals from 66 collections sites. The 3 most common haplotypes have a strikingly disparate geographical distribution. Two of them are nearly exclusive to the eastern part of the range while the third is restricted to the western part of the range. The haplotype boundary in east-central Illinois is very sharp. Genetic distance calculations divide the haplo- types into two main groups diverging by about 1.7%. The genetic distance partially correlates with the geographic distribution. We also report the discovery of two very distinct strains of Wolbachia in adjacent geograph- ical populations of NCR. In Diabrotica, Wolbachia has been identified as the agent primarily responsible for maintaining a breeding barrier between two differently colored subspecies, the Western Corn Rootworm (Diabrotica virgifera virgifera), WCR and the Mexican Corn Rootworm (D. v. zeae). PCR with Wolbachia-specific primers was used test for the presence of Wolbachia on either side of the NCR mtDNA boundary. 205/311 NCR gave a positive test for Wolbachia with 16S rDNA primers. A Wolbachia +/- boundary was found about 50-70 miles north and west of the mtDNA divide. A 1058 bp segment of the Wolbachia ftsZ gene was sequenced. Sequences from east of the mtDNA boundary are nearly identical to Wolbachia from WCR (<0.3%), whereas sequences from west of the mtDNA dividing line are very different (3.1%). Overall mtDNA diversity is substantially lower in both Wolbachia infected regions. These infections correlate with and are likely responsible for observed mtDNA genetic boundary with the clash of two incompatible Wolbachias preventing any significant introgression.