Phylogenomic characteristics of insect-associated rickettsiae. (A) Estimated phylogeny from an exhaustive search under parsimony of 731 core rickettsial proteins, with branch support from one million bootstrap replicates (redrawn from [22]). Ancestral group (AG) (red on the web figure) rickettsiae, typhus group (TG) (teal) rickettsiae, transitional group (TRG) (blue) rickettsiae, and spotted fever group (SFG) (brown) rickettsiae. Dashed box encloses the three representative insect-associated Rickettsia species. (B) Intersection of the unique R. typhi, R. prowazekii and R. felis genes that are not found in tick-associated Rickettsia. Data are from protein family clustering [22]. (C) List of genes shared exclusively by TG rickettsiae and insect-associated rickettsiae. Further descriptions of the shared RiOGs are posted at the PATRIC website [39].