Distribution of Wolbachia among the guild associated with the parthenogenetic gall wasp Diplolepis rosae

Symbionts of the genus Wolbachia, which cause reproductive alterations in insects, are suspected to pass regularly from one host lineage to another. One possible route for such 'horizontal transmission' is via parasitization. Here, we study this hypothesis in a complex guild of specialized parasitoids and inquilines, associated with the parthenogenetic, Wolbachia-infected gall wasp Diplolepis rosae. Diplolepis rosae galls ('bedeguar galls') were collected at three localities in The Netherlands and Germany. Specimens of most guild members were obtained. Using molecular techniques, the presence of Wolbachia was detected in five members of the assemblage. Three of these, Torymus bedeguaris, Habrocytus bedeguaris and D. rosae carried a Wolbachia belonging to the same subgroup (type I). A phylogenetic analysis was performed on DNA sequences from the FtsZ gene from these three Wolbachias. The analysis showed that the three strains do not cluster closely together, which indicates that the parasitoids have not acquired their Wolbachia from their host. We could not detect host-to-parasitoid transmission in this assemblage (where interactions are both specific, frequent, and possibly ancient).