Evidence for recombination between feminizing Wolbachia in the isopod genus Armadillidium

Wolbachia are maternally inherited endosymbiotic alpha-Proteobacteria infecting a wide range of arthropods. Wolbachia induce feminization in many terrestrial isopod species, particularly in the genus Armadillidium (Crustacea, Oniscidea). The diversity of Wolbachia strains infecting Armadillidium species was examined. Results reveal that natural populations of A. vulgare contain three different Wolbachia strains (wVulC, wVulM and wVulP). The wsp gene and its 3'-adjacent region show evidence that two recombination events have occurred between two of these strains. In both cases, multiple statistical analyses suggest that a small gene fragment of a strain closely related to wVulM (minor parent) is inserted into the genome of another strain closely related to wVulC (major parent). Although multiple infections in a single individual have never been demonstrated in natural population, the existence of recombination between feminizing strains suggests that bi-infections are possible, or at least that bi-infections can be maintained sufficiently long enough to allow recombination. Recombination events increase genetic diversity of Wolbachia found in Armadillidium species and may play a role in the ability of Wolbachia strains to invade new hosts.