Fig. 1

An example showing that one resolution of a multifurcation can be optimal for species mapping while another may be optimal for syntenic region mapping. a A gene tree with six leaves labeled with their syntenic regions. b A species tree. The tip association is \(\phi (g_i) = s_i\), \(1 \le i \le 6\). c A binary resolution of the gene tree in which the optimal species mapping cost is necessarily greater than the origin cost O since this tree is not isomorphic to the species tree; the optimal number of rearrangements in this case is 1. d Another binary resolution of the gene tree in which the optimal species mapping cost is just the origin cost O since this tree is isomorphic to the species tree; the optimal number of rearrangements in this case is 2