Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2010
Publication Date: 2/4/2011
Citation: Bouwma, A., Shoemaker, D.D. 2011. No Evidence for Wolbachia Phenotypic Effects in Newly Mated Queens of the Fire Ant Solenopsis invicta (Hymenoptera: Formicidae). Journal of Insect Science. 2:1-19. Interpretive Summary: Fire ants are considered significant ecological, agricultural, and public health pest throughout their invasive range in the U.S.A. Previous studies have demonstrated that individuals from native populations of fire ants commonly harbor Wolbachia bacteria that are known to induce a number of phenotypic effects in other insects and may be useful for biological control of insects. A scientist at the Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, Gainesville, Florida and a scientist from the University of Florida describe here the results of a study examining the productivity and brood production patterns of newly mated fire ant queens to determine what effects, if any, these bacterial infections have on these ants. Surprisingly, we found no evidence for significant effects. Future research is needed on other Wolbachia bacteria variants infecting fire ants to determine the extent of diversity of their effects on fire ants and to provide insight into the nature of selection on these bacteria in ants.
Technical Abstract: Wolbachia are intracellular bacteria that commonly infect many arthropods and some nematodes. In arthropods, these bacteria often induce phenotypic effects that enhance their own spread within host populations, despite sometimes also having deleterious effects on host fecundity and viability. Wolbachia surveys have found infections to be exceedingly common in ants, but little is known at this juncture as to what phenotypic effects, if any, they induce in this group. Previous studies have demonstrated that individuals from native populations of the invasive fire ant Solenopsis invicta commonly harbor one or more of three Wolbachia variants. One of the variants, wSinvictaA, typically occurs at low prevalence in S. invicta populations, appears to have been transmitted horizontally into S. invicta three or more times, and has been lost frequently from lineages over time. The low prevalence and instability of wSinvictaA infections in S. invicta raises the possibility that this Wolbachia variant has negative fitness effects on its fire ant hosts. We studied the productivity and brood production patterns of newly mated fire ant queens during simulated claustral founding to determine what phenotypic effects, if any, wSinvictaA infections have on these ants. Surprisingly, we found no evidence for Wolbachia-induced cytoplasmic incompatibility, sex-ratio distortion, or significant fitness effects. These results beg the question of how this variant is maintained in host populations.