Distribution and reproductive effects of Wolbachia in stalk-eyed flies (Diptera:Diopsidae)

Wolbachia are cytoplasmically inherited bacteria capable of altering the reproductive biology of their hosts in a manner which increases their spread within a population. These microbes can cause cytoplasmic incompatibility, parthenogenesis and feminization of genetic males. Because Wolbachia have been associated with female-biased sex ratio distortion, we used a PCR assay to examine 17 species of stalk-eyed flies (Diptera: Diopsidae), two of which exhibit female-biased sex ratios, for the presence of these microbes. Type A Wolbachia was detected in four diopsid species, three from the genus Sphyracephala, none of which exhibit biased progeny sex ratios. The reproductive effects of the microbe were examined in one of those species, S. beccarii, by conducting reciprocal crosses between infected and uninfected strains. In this species, Wolbachia do not cause detectable cytoplasmic incompatibility or reduce host fecundity. In contrast, our results are consistent with an association between the microbes and enhanced male fertility. Possible explanations for the pattern of distribution and effects on male fertility include a predisposition for acquiring Type A Wolbachia by these flics and accommodation by the host genome to bacterial presence.