Phylogenetic relationship between the tetranychid host species from which Wolbachia and Cardinium strains were obtained. Maximum likelihood cladogram (28S rDNA) of the genus Bryobia and four outgroup species of the genus Petrobia is shown . Tetranychus urticae was depicted separately as the exact position of T. urticae relative to the other host species was not studied so far. The genus Tetranychus belongs to another subfamily (Tetranychinae) than Bryobia and Petrobia (both Bryobiinae) of the family Tetranychidae. The mode of reproduction is given for each host species (A=asexual, S=sexual) in a separate column, and the subsequent columns indicate from which host species Wolbachia and or Cardinium strains were included in this study. Species names are colored as in Figure 2, 4, 5, and Additional file 3. Host species in grey were not included in this study. Numbers above branches (bold) indicate ML bootstrap values based on 1,000 replicates, numbers below branches (plain) depict Bayesian posterior probabilities (only values larger than 50 are indicted).