The influence of parthenogenesis-inducing Wolbachia on the oviposition behaviour and sex-specific developmental requirements of autoparasitoid wasps

Parthenogenesis-inducing (PI) Wolbachia are bacteria that cause incipient m ale eggs of parasitoid wasps to develop as females. These microbes may inva de populations and lead to fixation of parthenogenesis. In this study, the consequences of fixation of PI Wolbachia on evolution of behaviour and deve lopment were addressed in three species of whitefly parasitoids in the genu s Encarsia. Most sexual Encarsia are obligate autoparasitoids. In these haplodiploid wa sps, fertilized, female-producing eggs are laid in whitefly or scale insect nymphs, while unfertilized, male-producing eggs are laid in immature paras itoids within the homopteran integument. The oviposition behaviour and prog eny developmental requirements of unmated females of a sexual autoparasitoi d species were compared with two species that were fixed for PI Wolbachia. All species were treated with antibiotics, effectively 'curing' the asexual species of Wolbachia infection. As expected, unmated females of the sexual species, E. pergandiella, laid f ew eggs in whiteflies relative to immature parasitoids, and males emerged e xclusively from parasitoids. In contrast, females of one of the parthenogen etic species, E. formosa, laid few eggs in parasitoids relative to whitefli es, and male progeny emerged exclusively from whiteflies. Females of the se cond parthenogenetic species, E. hispida, were intermediate in their ovipos ition behaviour. Females laid eggs in both wasps and whiteflies. However, a ll of the males except one emerged from the whiteflies. The results suggest that the association of autoparasitoids and PI Wolbachia may result in dra matic evolutionary change of both host selection behaviour and developmenta l requirements of the infected wasps.