Phylogenetic stability of all gag and env phylotypes within subgroups. The gag Neighbor-Joining tree contains sequences representing the 21 gag phylotypes identified in Figure 2. The env Neighbor-Joining tree contains sequences representing the 16 env phylotypes identified in Figure 2. Numbers and letters located at outer taxonomic units represent phylotype designations in the gag and env trees, respectively. Numbers at internal nodes of the trees represent bootstrap values. Yellow and blue shaded regions represent subgroups 1 and 2, respectively, for both trees. Conflicting subgroup placement for gag phylotypes 10–14 relative to Figure 2 are represented with colored ovals. Scale bars represent substitutions per site.