⃛and discovered on Mount Kilimanjaro

Abstract

The endocytoplasmic bacterium Wolbachia causes the death of arthropod embryos, when present in reproductive organs, by cytoplasmic incompatibility¹. Wolbachia is harboured in both sexes but transmission is maternal only. Cytoplasmic incompatibility occurs when infected males inseminate uninfected females² or females bearing a different variant of Wolbachia³,⁴. Two kinds of Wolbachia have been described¹: (mod⁺resc⁺) which induces cytoplasmic incompatibility by modifying sperm but can rescue this phenotype when in the egg, and (mod⁻resc⁻) which neither induces cytoplasmic incompatibility nor rescues from it. Theory predicts a third kind (mod⁻resc⁺) that would not induce cytoplasmic incompatibility but would rescue from it^5,6,7. We have found such a Wolbachia variant in a Drosophila simulans population on Mt Kilimanjaro, Tanzania. The existence of a mod⁻resc⁺ Wolbachia shows that the modification and rescue functions can be dissociated with regard to the cytoplasmic incompatibility process.