Submitted to: Neotropical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2008
Publication Date: 12/1/2008
Citation: Copeland, C.S., Matthews, R.W., Gonzalez, J.M., Aluja, M., Sivinski, J.M. 2008. Wolbachia in Two Populations of Melittobia digitata Dahms (Hymenoptera: Eulophidae). Neotropical Entomology. 37(6):633-640. Interpretive Summary: Parasitoid wasps, a form of natural enemy used in biological control of pests, often have female biased sex ratios. If the reasons for this were better understood perhaps highly efficient all-female strains could be produced for mass-rearing and release on crops. One of the causes of biased sex ratios is a microbe named Wolbachia that causes male embryos to become females. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology with collaborators from Texas A&M University and the Mexican Instituto de Ecologia investigated two populations of the female-biased parasitoid Melittobia digitata to see if Wolbachia was present. The Wolbachia discovered belongs to new subgroup, one that was found to occur in a number of very distantly related insects and other animals. This suggests that it moves easily from one host to another and might be a candidate to artificially produce females in other wasps.
Technical Abstract: Melittobia sp. (Eulophidae), gregarious parasitoids of various species of bees, wasps, and flies, exhibit among other characteristics highly female-biased sex ratios. Several factors have been proposed that could give rise to these distorted sex ratios, including lethal male combat, inheritance asymmetry related to inbreeding, and sex ratio distorting endosymbionts, including Wolbachia endosymbionts. We investigated two strains of Melittobia digitata in search of Wolbachia infection. PCR based amplification of the Wolbachia surface protein gene (wsp) confirmed that Wolbachia does indeed infect M. digitata. Further, examination of these wsp sequences revealed that these Wolbachia appear to form a unique subgroup, denoted here as Dig, within the B supergroup of Wolbachia endosymbionts. Known hosts for the lineage including this subgroup are distantly related, supporting the hypothesis of horizontal rather than vertical transmission for this lineage of Wolbachia.