A stable triple Wolbachia infection in Drosophila with nearly additive incompatibility effects

Drosophila simulans strains infected with three different Wolbachia strains were generated by experimental injection of a third symbiont into a natura lly double-infected strain. This transfer led to a substantial increase in total Wolbachia density in the host strain. Each of the three symbionts was stably transmitted in the presence of the other two. Triple-infected males were incompatible with double-infected females. No evidence was obtained f or interference between modification effects of the different Wolbachia str ains in males. Some incompatibility was observed between triple-infected ma les and females. However, this incompatibility reaction is not a specific p roperty of triple-infected flies, because it was also observed in double-in fected strains.