All other allelic variants differed from the founder alleles at four or more sites and were considered as putative recombinational imports. Ignoring alleles with one non-unique

and two nucleotide changes, the estimated ratio of recombinational events to mutational events per gene fragment is 11:1. If we include non-unique changes as recombinational imports, and unique changes as point mutations, the ratio is 15:2. We therefore conclude that new alleles were 7.5 to 11 times more likely to be generated by recombination than by point mutation. This is a conservative estimate because single nucleotide changes were attributed to point mutation and not to recombination, although recombination between similar Dinaciclib alleles could result in a single nucleotide change. Further, a high rate of recombination is consistent with the observed incongruence between the four gene tree topologies (Additional file 3). Intragenic recombination is another process that may contribute to the origin of new Wolbachia genotypes. We detected intragenic recombination within the trmD and wsp genes (Figure 3). The alignment of wsp genes shows that the polymorphic sites are not randomly distributed, but clearly shows a mosaic pattern consistent with recombination. Intragenic recombination is not restricted to Wolbachia strains from the same host

species, but also involves strains infecting different host species. For example, the wsp sequence obtained from Wolbachia in B. sarothamni (all populations) is a recombinant between selleck the wsp sequences obtained from Wolbachia in B. kissophila (FR13) and T. urticae (T3) (Figure 3). Cospeciation of Wolbachia

and host species Examination of the concatenated Wolbachia phylogeny reveals that there is generally a lack of cospeciation between host and parasite (Figure 4). Wolbachia strains obtained from a single host species do not clearly cluster. For example, strains from B. rubrioculus are found at different places in the phylogeny. The same is true for strains from B. spec. I. On the other hand, the Wolbachia phylogeny is not completely random with respect to host species. Some Wolbachia strains from B. kissophila cluster together, whilst others Thalidomide cluster with strains from B. spec I (BEL4_2) or B. rubrioculus (FR15). Two B. kissophila-derived strains (NL9 and FR13) are very divergent from all other B. kissophila strains. In the exceptional case of B. sarothamni, the same Wolbachia genotype was found in all five populations (from Belgium and France; except for a minor difference in trmD for BEL6; Figure 2, 4, and Table 2). This strain was not found in any of the other species, although it closely resembles the Wolbachia strain infecting B. berlesei at three of the four genes (wsp is highly divergent between the two strains). Bryobia sarothamni and B.