Figure 4

Cases in which agreement subtrees must be taken. (a) HGT case: An HGT event occurred in the blue gene, from the edge leading to 2 to the one leading to 3. While the red gene is unaffected, the blue gene has 2 and 3 as sister taxa. (b) Missing taxa case: Taxon 3 is missing the blue gene. In both cases (a) and (b), a tree over taxa {1,2,4} has the same topology.