Wolbachia wsp Gene Clones Detect the Distribution of Wolbachia Variants and wsp Hypervariable Regions Among Individuals of a Multistrain Infected Population of Diabrotica barberi (Coleoptera: Chrysomelidae)

The northern corn rootworm (Diabrotica barberi) in eastern and central North America exhibits at least three distinct populations with respect to Wolbachia infection: uninfected; singly-infected; multi-infected. The infected states are associated with different mtDNA haplotypes and reduced mtDNA variability. Sequences of the Wolbachia wsp surface protein gene indicated that multiple infections exist that include at least five distinct strains which are supported by both nucleotide analysis and digital translation alignments. The recovery of the different wsp hypervariable regions among 55 clones obtained with universal PCR primers from several individuals was unequal. The most common was obtained 33 times, the least common only once. One of the Wolbachia strains is present in both single infected and multiple infected individuals. Possible explanations for the frequency differences are that the frequency of each strain is not the same within each insect. An alternative possibility is that not all individuals are infected with all five strains and that different animals contain different combinations of the strains. The second scenario suggests that some strains are rare in the population. The two explanations are not mutually exclusive. Comparisons of the wsp genes with sequences in GenBank show that two of the strains are most similar to strains infecting subspecies of the congeneric western corn rootworm (D. virgifera virgifera and D. v. zeae). The most similar sequence to a third strain is found in a spider. Individual wsp hypervariable regions (HV)(some literature uses HVR for these regions) were also aligned with database sequences. The results provide evidence that some HVs are much more common than others and that the HVs can be shuffled to create new wsp genes.