Taxon coverage and defining trees. A. For the original tree and partial taxon coverage shown on the left, the two induced subtrees (middle) do not define the original tree, because other trees (right, middle and lower) also display these subtrees. B. In this case, the middle two subtrees do define the original tree. Notice that the taxon coverage pattern is the same in both cases. This coverage is phylogenetically decisive for the original tree in B, but not in A. Thus, it follows that this taxon coverage is not phylogenetically decisive for all trees.