Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2001
Publication Date: 11/1/2001
Citation: Interpretive Summary: The immature stages of three species of beetles, commonly called corn rootworms, are major pests of corn. Corn rootworms are responsible for an estimated $1 billion in annual losses to the U.S. corn industry. Yet several species of beetles that are closely related to corn rootworms and occur in the same locale have not developed into pests. Recently it has been shown that infections by bacteria can disrupt the reproductive compatibility within a species and it has been suggested that these infections may lead to the development of new species. We investigated if the presence of bacteria, in the genus known as Wolbachia, could be implicated in the reproductive incompatibility of some of these closely related beetles. We used the molecular genetic techniques of directed polymerase chain reactions, restriction fragment length polymorphisms, and DNA sequencing to detect and categorize bacteria in 14 related beetle species representing two genera, including the three species of corn rootworms. We found Wolbachia infections in five of the beetle species, including one of the corn rootworms, representing both genera. We found that four of the beetle species, including the corn rootworm, were infected with the same type of bacteria while one species had a different type. We are unsure of the significance on the beetles of these two different types of bacteria. But these bacterial infections, at least in part, may be responsible for the many species of closely related beetles. Also, these bacterial infections may currently be acting towards development of more new species. As our technology matures, we may be able to use these bacteria to our advantage in combating these pests.
Technical Abstract: Wolbachia are a rickettsial type bacteria that have been implicated as a cause of reproductive disruption and alteration in many insect species. PCR assays of the 16S rRNA gene were conducted to reveal the prevalence of Wolbachia in 14 Diabroticite species, 12 Diabrotica and 2 Acalymma. Assays revealed the presence of Wolbachia infection in 3 Diabrotica; D. virgifera virgifera LeConte, D. cristata (Harris), D. lemniscata LeConte, and the 2 Acalymma; A. blandulum (LeConte ), A. vittatum (Fabricius) species assayed. Subsequent assays of positive individuals by sequencing of the 16S rRNA and ftsZ genes as well as restriction digests of the ftsZ gene were performed to ascertain the identity of the Wolbachia strain infecting the positive Diabroticites. Distances and neighbor-joining trees on the Kimura 2- parameter measure as well as BlastN searches in GenBank revealed that the strain of Wolbachia infecting D. lemniscata, D. v. virgifera, A. blandulum, ,and A. vittatum are most likely the same strain of Wolbachia within the division A group. The strain infecting D. cristata, while a division A strain, is different from the Wolbachia infecting the other four Diabroticites. Implications of these infections are also discussed.