FIG. 3.

Mappings from transfer events. Assuming that transfers, duplications, and losses have an equal cost, any optimal reconciliation of G and S must have a cost of 2. The figure depicts two such optimal reconciliations, one in which the transfer node maps to species A and one in which it maps to the species represented by lca(A,B). These two mappings are shown by the dashed blue lines. All other nodes have identical mappings in the two reconciliations. Both reconciliations have one loss and one transfer, and the reconciliation in which the transfer node maps to lca(A,B) shows that transfer node mappings are not constrained in the manner of speciation or duplication nodes as shown in Theorem 4.1.