Polygalacturonase family tree. Four monophyletic clades (blue, pink, green, and yellow clouds) contain monocot, eudicot, Selaginella, and Physcomitrella genes. The tree contains two large polytomies, indicated in light grey and labeled “A” and “B”. Polytomy B contains unresolved Physcomitrella and Selaginella members. The algal root gene is from C. reinhardtii, a chlorophytic alga.