FIG. 6.

SERA sequences belong to one of two major phyletic groups that separate according to their catalytic residues. Colored segments that make up the inner disc delineate active-site and secondary-site mutations in SERA sequences. Colored segments that are part of the outer ring mark the clade to which sequences belong. Thick lines in the phylogeny indicate branches shared by MCMC, maximum-likelihood, and neighbor-joining topologies. Thin lines indicate branches supported by MCMC and one other method. Dashed lines indicate branches existing only in the MCMC topology. MCMC branch probabilities are given on the appropriate branches where they are less than 1. Members of the genus Theileria appear to have a single-copy SERA, the only observation to date of a SERA ortholog outside the genus Plasmodium. Radiation in SERA sequences containing the serine active-site mutation tends to be species specific, whereas radiation of cysteine SERA sequences has occurred prior to speciation. Branch lengths for SERA6 and SERA7 tend to be shorter than those of serine-type SERAs and those of SERA8.