Note that with a practical upper limit of 25 taxa for which trees can be tested exhaustively, additional criteria or assumptions must be introduced. All available algorithms may fail to find the best tree. Unrooted trees can be inferred from other kinds of evidence, such as chromosomal inversions in Hawaiian fruitflies or comparative anatomy in the mammal-like reptiles. This section celebrates some classical examples of phylogenetic inference. The Drosophila example is especially elegant.
Flies have wonderfully large, banded chromosomes.
Since each chromosomal inversion is a good, reliable synapomorphy, a precise phylogeny could be inferred at the species level. Some molecular evidence can only be used to infer phylogenetic relations with distance statistics. Direct sequence comparison is a powerful method with increasing popularity. The older molecular techniques, immunological cross-reactivity and DNA annealing temperatures, give measures of similarity that cannot be analyzed cladistically. Comparing molecular evidence and paleontological evidence.