Blochmannia phylogeny estimated from a region of the 16S rDNA gene, analyzed without outgroups. The analysis includes 50 new bacterial sequences from Camponotini and 28 published Blochmannia sequences. Taxon groups are labeled by the ant host from which the bacterial gene was amplified. The phylogeny was estimated using Bayesian methods, and the topology shown reflects the majority-rule consensus of post-burnin trees. Both this unrooted and rooted (Figure 3) phylogenies resolved four major lineages within Blochmannia: Polyrhachis, Colobopsis, Opisthopsis, and a fourth group composed of Camponotus, Calomyrmex, and Echinopla. In this unrooted tree, only the posterior probabilities of major nodes are marked. Relationships within major groups resemble those in the rooted tree (Figure 3). Taxon names were removed for clarity, and we refer the reader to the rooted tree for these data.