Effects of parasitic sex-ratio distorters on host genetic structure in the Armadillidium vulgare-Wolbachia association

In the pill bug Armadillidium vulgare (Crustacea, Oniscidea) Wolbachia facilitates its spread through vertical transmission via the eggs by inducing feminization of genetic males. The spread of feminizing Wolbachia within and across populations is therefore expected to influence mtDNA genetic structure by hitchhiking. To test this hypothesis, we analysed nuclear and mtDNA genetic structure, and Wolbachia prevalence in 13 populations of the pill bug host. Wolbachia prevalence (ranging from 0 to 100% of sampled females) was highly variable among populations. All three Wolbachia strains previously observed in A. vulgare were present (wVulC, wVulM and wVulP) with wVulC being the most prevalent (9 out of 13 populations). The host showed a genetic structure on five microsatellite loci that is compatible with isolation by distance. The strong genetic structure observed on host mtDNA was correlated to Wolbachia prevalence: three mitotypes were in strong linkage disequilibrium with the three str...