The research of two Dutch entomologists, Richard Stouthamer and Menno Schilthuizen of Wageningen Agricultural University, reveal that some insects, parthenogenesis (in which females give rise only to daughters and no males are born) not for their best interest, but because of a parasite. A bacterium called, Wolbachia infects perhaps 16% of all insect species by altering its hostís sex life and reproduction for the parasiteís benefit. In wood lice, for example, the bacterium manages to transform infected males into functional females.
Unfortunately, researchers have not been successful at re-creating in the lab, how the bacterium can jump from one species to another, in mosquitoes and flies, to infect them. This process is called horizontal transmission. The two Dutch entomologists hypothesized that the process of horizontal transmission is caused by cospeciation (pairing two species). However, their research that consisted of collecting 20 wasp species that carried Wolbachia and studying their DNA regions did not work. Their findings were not consistent since the bacterium in wasp species did not diverge.
Henk Braig of the Yale University School of Medicine, like many Wolbachia researchers are eager to know how this parasite can also cause cytoplasmic incompatibility (prevent some mating pairs from having viable offspring). They are trying to unravel the molecular mechanism by which the bacterium manipulates its host, and whether the bacterium really harms its hosts by making them asexual. Researchers in evolutionary biology will continue their quests in dissecting a better understanding of the bacterium since more and more species are being infected. Some of the recent victims are crustaceans, mites, and even nematode worms. More importantly, research on the Wolbachia phenomenon may offer practical benefits in pest control, as well as a whole new perspective on being able to make insects parthenogentic at our will. It will be interesting to find out how extensive asexual reproduction will catch on to other species.
Enserink, Martin. (1997, March 21). Thanks to a Parasite, Asexual Reproduction Catches On. Science, vol. 275 pp. 1743.