Male–killing Wolbachia in two species of insect

Gregory D. D. Hurst, Francis M. Jiggins, J. Hinrich Graf von der Schulenburg, Dominique Bertrand, Stuart A. West, Irina I. Goriacheva, Ilia A. Zakharov, John H. Werren, Richard Stouthamer, Michael E. N. Majerus

Abstract

The inherited bacterium Wolbachia spreads through the manipulation of host reproduction, and has been suggested to be an important factor in arthropod evolution, from host speciation to the evolution of sex–determination systems. Past work has shown that members of this group may produce cytoplasmic incompatibility, feminize genetically male hosts, and induce host parthenogenesis. Here, we report an expansion of the range of reproductive manipulations produced by members of this clade, recording Wolbachia strains that kill male hosts during embryogenesis in two host species, the ladybird Adalia bipunctata, and the butterfly Acraea encedon. Both male–killing bacteria belong to the B group of Wolbachia. However, phylogenetic analyses were unable to resolve whether the bacteria in the two species are monophyletic, or represent independent origins of male–killing among the B–group Wolbachia. We also found significant divergence within the wsp gene of Wolbachia strains found in different A. bipunctata individuals, suggesting this host species contains two Wolbachia strains, diverged in wsp sequence but monophyletic. Our observations reinforce the notion that Wolbachia may be an important agent driving arthropod evolution, and corroborates previous suggestions that male–killing behaviour is easily evolved by invertebrate symbionts.