Diversity of Wolbachia endosymbionts in heteropteran bugs

An extensive survey of Wolbachia endosymbionts in Japanese terrestrial heteropteran bugs was performed by PCR detection with universal primers for wsp and ftsZ genes of Wolbachia, cloning of the PCR products, restriction fragment length polymorphism analysis of infecting Wolbachia types, and molecular phylogenetic characterization of all the detected Wolbachia strains. Of 134 heteropteran species from 19 families examined, Wolbachia infection was detected in 47 species from 13 families. From the 47 species, 59 Wolbachia strains were identified. Of the 59 strains, 16 and 43 were assigned to A group and B group in the Wolbachia phylogeny, respectively. The 47 species of Wolbachia-infected bugs were classified into 8 species with A infection, 28 species with B infection, 2 species with AA infection, 3 species with AB infection, 5 species with BB infection, and 1 species with ABB infection. Molecular phylogenetic analysis showed little congruence between Wolbachia phylogeny and host systematics, suggesting frequent horizontal transfers of Wolbachia in the evolutionary course of the Heteroptera. The phylogenetic analysis also revealed several novel lineages of Wolbachia. Based on statistical analyses of the multiple infections, we propose a hypothetical view that, in the heteropteran bugs, interactions between coinfecting Wolbachia strains are generally not intense and that Wolbachia coinfections have been established through a stochastic process probably depending on occasional horizontal transfers.