Evolution of the repeat sequences in M. haemolytica. Maximum-parsimony tree of the two distal repeat units from each promoter (A) and repeat tract polymorphisms (B) using M. haemolytica strains, which represent the diversity within this species based on MLEE, geographic origin, and host association. See the text for clusters I, II, and III. The green and red boxes highlight polymorphic sites that match and differ, respectively, from the consensus sequence. The number of repeat units per promoter is indicated. Sequence names contain the strain ID and abbreviations of the corresponding MLEE lineage (A, B, or C).