Symmetric Tree

Phylogenetic trees can have varying levels of symmetry, from highly asymmetric trees whose branches lie mostly to one side of each node, to highly symmetric trees of \(2^k\) leaves, each separated from the root by the same number of nodes.

The level of symmetry in a phylogenetic tree contains information about the evolutionary process that has given rise to the tree. Symmetry in trees is used to examine if descendant species inherit their speciation rates from ancestral species, potentially producing considerable asymmetry. When each species is equally likely to be the next to speciate, however, the probability can be greater that the evolutionary process produces symmetric trees.