Irreversible thelytokous reproduction in Muscidifurax uniraptor

Vertically transmitted bacteria of the genus Wolbachia are obligatory endosymbionts known to cause thelytokous (asexual) reproduction in many species of parasitic Hymenoptera. In these species production of males can be induced, but attempts to establish sexual lines have failed in all but one genus. We have found three reproductive barriers between antibiotic-induced males and conspecific females of Muscidifurax uniraptor Kogan and Legner (Hymenoptera: Pteromalidae): males do not produce mature sperm, females are reluctant to mate, and a major muscle is absent from the spermatheca. These findings suggest that Wolbachia-induced thelytokous reproduction in M. uniraptor is irreversible, and are consistent with the idea that since sexual reproduction has ceased, selection on sexual traits has been removed leading to the disappearance or reduction in these traits. Because under these circumstances asexual reproduction is irreversible, the host has become totally dependent on the symbiont for reproduction.