Positive selection characteristics for the env gene in each cluster.

a Model code in PAML (see Methods).b the likelihood ratio test statistics (2 delta lambda statistics).c The P values indicate the level of significance with a χ2 distribution and degrees of freedom = 2.d Associated average dN/dS (ω) of positions under positive selection.e Codons with a high posterior probability (PP > 0.90) that supports the likelihood of a site having a dN/dS > 1.Positive selection characteristics for the env gene in each cluster.