Model comparisons and parameter estimates under models of constant (H0) or variable �� rate ratios across branches (Br), clades (H1 to H3) or both clades and sites (A and B) for the �� subunit.

Notes�C?: log-likelihood value; HA: alternative hypothesis to the current model; ��0: background rate; ��1�C5: branch/clade specific rates as indicated in Figure 4; p0�C2: proportions of sites in each rate category. The hat notation indicates parameters that are free to vary. Positively selected sites were identified with BEB and NEB between brackets for model A and NEB only for model B; a 95% cut-off level of posterior probability was used. Sites putatively under positive selection are numbered according to the human �� reference sequence (accession numbers HSU66661/AAB49284). ?: these sites were putatively identified with a posterior probability >50% (see text). The underlined sites are those common to both model A and model B. Curly braces indicate equally parsimonious ancestral sites.