Northern corn rootworm (Diabrotica barberi) populations infected by at least five Wolbachia strains

Wolbachia infections are present in northern corn rootworm (Diabrotica barberi) populations from east of the Mississippi River. The boundary between infected and uninfected populations is in central Illinois. DNA sequencing of Wolbachia ftsZ and wsp segments indicates that east central Illinois populations are infected with a single strain of Wolbachia. From eastern Illinois and eastward, multiple strain infection appears to be the rule. To estimate the number of Wolbachia strains that might be present, multiple clones from the wsp and MLST (Multi Locus Strain Testing) loci were sequenced from several beetles. For the ftsZ locus 84 clones were distributed among 3 sequence groups indicating 3 strains. The number of clones and strains for the other loci were: coxA 25/3 or 4?; hcpA 48/3; fpbA 36/4; gatB 50/5. In wsp each of four hypervariable (HV) regions were scored separately from 56 clones. HV1 had 3 sequence groups, HV2 had 5, and HV3 & HV4 had 4 each. The results support the contention that the populations of northern corn rootworm east of the mtDNA boundary are infected by at least 5 strains of Wolbachia (wsp and gatB. Wolbachia infections may facilitate reproductive isolation of populations that cold be an early step towards speciation.