One characteristic of inferred phylogenetic trees is their shape. Rooted binary trees are more balanced, or symmetric, to the extent that sister groups contain similar number of leaves. Premised on the idea that macroevolutionary processes may leave a strong signature in the shape of phylogenetic trees, inferred tree shapes can be compared to expectations under probabilistic models of speciation and extinction in an attempt to make macroevolutionary inferences (e.g. Harvey and Purvis, 1991; Kirpatrick and Slatkin, 1993; Guyer and Slowinski, 1993; Mooers and Heard, 1997; Bortolussi et al., 2006)
