Phylogenetic tree derived from the Basic matrix (1222 positions) under ML criterion. Names of the taxa clustering within the Arsenophonus clade are printed in colour: red for the long-branched taxa, dark orange for the short-branched taxa. The arrows point to the new sequences obtained in our study. Different types of sequences determined from the specimens of O. avicularia are designated by the numbers with asterisks. The type species A. nasoniae is designated by the orange asterisk. Solid circles on branches label the clusters strictly concordant with the host phylogenies. Open circles designate host-specific lineages without coevolutionary signal. Solid vertical lines indicate reciprocally monophyletic groups of symbionts and hosts. Dashed lines show paraphyletic symbiont clades restricted to monophyletic host groups. Names in the brackets indicate host taxa. "Symb-" in the taxon designation stands for "Symbiotic bacteria of". Bars represent GC content of each taxa. Complete information on the sequences is provided in the Additional file 5.