Trails of destruction for two pairs of six-taxon trees. Two pairs of reference and test trees are shown: in both cases, the test tree is the consequence of two edit operations on the corresponding reference tree. The edits are indicated with boldface arrows, with the arrowhead pointing to the recipient lineage. The trails of destruction are composed of the edges in each reference or test tree which imply bipartitionings of taxa that are incompatible with the other tree. These incompatible edges are drawn with dashed lines in the figure, and the endpoints indicated with filled circles. In Figure 8a, there are four endpoints on the trail of destruction, thus identifying the minimum number of edit operations as 2. The trail in Figure 8b has only two endpoints, so in this case the minimal edit distance of 1 suggested by the endpoints is not the correct number of edits.