Compares the topologies of the source and the destination tree.
For each subtree of the destination tree, the best matching subtree in the source tree is searched.
If any source subtree contains the same set of species (while disregarding the subtree topology itself), the destination subtree parent branch will not get any annotation.
Otherwise the number of differences (i.e. the number of missing plus additional species) to the best matching source subtree is written to the destination subtree parent branch.