Comparing Trees Via Crossing Minimization

Abstract

Two trees with the same number of leaves have to be embedded in two layers in the plane such that the leaves are aligned in two adjacent layers. Additional matching edges between the leaves give a one-to-one correspondence between pairs of leaves of the different trees. Do there exist two planar embeddings of the two trees that minimize the crossings of the matching edges ? This problem has important applications in the construction and evaluation of phylogenetic trees.