Phylogenetic trees, by definition, cannot represent ancestral nodes because we do not have the DNA of our direct ancestors. By and large, we only have the DNA of living species, so we use comparative analyses of DNA differences to establish the most likely branching tree that led to present distributions. Similarly, it cannot tell us whether there is a tree in the first place, because that is not its job. Its job is to sort through the similarities in sets of data to determine what order those sets most likely branched out from each other in.