Summary of the phylogenomic analyses showing the species distribution of various α-proteobacteria-specific proteins and the suggested evolutionary stages where the genes for these proteins have likely evolved. The genes IDs for some proteins described in earlier work are indicated . The information for all other proteins can be found in the indicated Tables or Additional files. A large numbers of conserved indels that are specific for different groups or clades within α-proteobacteria shown here have also been identified in our earlier work  (not shown here). The branching order of α-proteobacteria relative to other bacteria has been established in earlier work [32,58].