Phylogeny of Rickettsia. The name of the host prefixed by (s) is given where the bacterium does not have a species name, as well as names for each Rickettsia group, life history and host order. (a) Bayesian phylogeny using concatenated sequences of atpA, coxA, gltA, 16S. Posterior support for each node is shown. (b) Maximum likelihood phylogeny based on complete sequences of atpA, coxA and gltA. Bootstrap support is given as a percentage above the node, and posterior support from a Bayesian tree is given as a decimal below the node. aPreviously characterised groups. bOnly circumstantial evidence connects the trait to the strain.