Wolbachia from Drosophila incompta: just a hitchhiker shared by Drosophila in the New and Old World?

Wolbachia are intracellular endosymbionts that infect arthropods and filarial nematodes, occasionally causing a wide variety of modifications in host biology, such as male-killing and cytoplasmic incompatibility (CI), amongst others. This study assembled draft genomes for Wolbachia infecting Drosophila incompta, a species that uses flowers as exclusive breeding and feeding sites, in two distinct Brazilian populations. The absence of four genes involved in CI from this genome, together with literature reports of low frequencies of infected flies in wild populations that contain high mitogenome polymorphism, suggests that this bacterium does not induce CI in D. incompta. Phylogenomic analysis placed Wolbachia infecting D. incompta as closely related to the wMel strain which received such name since it was originally detected in Drosophila melanogaster. In addition, phylogenetic analysis using the Wolbachia surface protein gene and five genes used for multilocus sequence typing of Wolbachia found infecting Drosophila and other arthropod species of Old and New World displayed a complex evolutionary scenario involving recent horizontal transfer bursts in all major clades of Wolbachia pipens belonging to the supergroup A in both geographical regions.