(A) Cladogram of 20 primate viperin genes sequenced for the evolutionary analyses. Free ratio analysis in PAML was used to calculate the ω (dN/dS) ratios of individual branches. The corresponding ω ratios are shown above each branch, and the number of non-synonymous changes and synonymous changes are indicated in parentheses. Branches with ω > 1 are highlighted in bold. In the case of no observed synonymous changes, the ω ratio could not be calculated (indicated by 'inf'). (B) Likelihood ratio test statistics for models of variable selective pressures along branches of primate viperin genes are shown, using a comparison between M0 (same dN/dS ratio for all branches) and M1 (different dN/dS ratio for each branch, free-ratio). (C) A schematic of Viperin protein domain structure is shown. Residues under positive selection with high confidence (P > 0.95) are indicated in symbols above the protein. The table summarizes the likelihood ratio test statistics for models of variable selective pressure among viperin sites (M7 vs M8). Similar results were obtained in a comparison of M1 (neutral) versus M2 (selection) (data not shown). The amino acid positions are annotated in reference to the human Viperin sequence. (D) The table summarizes likelihood ratio test statistics performed between the M7 (neutral) and M8 (selection) models for the individual protein domains of viperin gene from 20 primate species.