Phylogenetic analysis by maximum likelihood estimation of the primate SAMHD1 genes.

lnL, log-likelihood value. 2Δl, the likelihood ratio test statistics (2 delta lambda statistics). The P values represent a level of significance with a χ2 distribution and degrees of freedom = 2 (M1a vs. M2a and M7 vs. M8). Positively selected sites (PSS) were identified with posterior probability (p)≥0.90. One asterisk indicates posterior probability p≥0.95 and two asterisks p≥0.99. The null models do not allow for a site with ω>1. The amino acid sequence of human SAMHD1 was used as the reference standard. The results from M3 (discrete) are not shown since M3 can overestimate the number of positively selected sites.