Simplification of an ABC gene tree, example for erroneous input data that cannot be corrected. The original tree is shown on top, the automatically simplified tree at the bottom. Here, the manual simplification in  went much farther by treating human ABCD1 and ABCD2 (arrows) as classified consistently since both are due to a recent duplication. In fact, the existence of a single mouse homolog indicates that in fact, ABCD1 and ABCD2 should be denoted ABCD1a and ABCD1b. In that case the automatic simplification would match the manual one since the classification hierarchy is ignored after the subsubfamily level, compressing the entire subtree to a single "Bilateria ABCD" leaf, except for the fly sequences at the root of the subtree.