Evolutionary relationships between mother and child env sequences. A maximum likelihood phylogenetic tree was constructed using alignments of clonal env sequences obtained from the children in successive years and from their mothers with reference sequences from HIV-2 groups A, B and G. The bootstrap values supporting the internal branches are shown as follows: * bootstrap >70, ** bootstrap >90. The scale bar represents evolutionary distance in number of substitutions per site. Sequences from child 1 (PTHDECT) are represented by red ircles, with each year of sample collection in orange (1998), red (2000) and dark red (2003); sequences from mother 1 (PTHCC20) are represented by green circles, with each of sample collection in light green (2000) and dark green (2003); sequences from child 2 (PTHDESC) are represented by blue squares with each year of sample collection in light blue (1992), blue (1997) and dark blue (2001); sequence from mother 2 has been published before  and is represented by a pink square. The tropism of the viruses is indicated to the right of each cluster.