GAUT superfamily tree. In this tree, phylogenetic distance is indicated by branch length. The GATL gene family (yellow cloud) is well-supported as being derived from within the GAUTs; due to a polytomy in the GATL family, clade relationships within this family are not well resolved. The distance of the GATLs from the GAUTs suggests an ancient divergence, but the position of the algal root supports the hypothesis that the GATLs descended from the GAUTs rather than diverging from a common ancestor. Scale bar, 0.7 substitutions/site.