Phylogenetic Trees. Numerical taxonomy. Awash in Molecular Data. Zuckerkandl and Pauling (1965) Originated Molecular Clock Basic flavors of tree construction Distance Matrices ( eg Neighbor Joining) Parsimony Conserved Indels. Distance Matrices.
Note that while maximum parsimony supports the WY grouping, the few number of informative sites makes it impossible to separate X from Z. In fact, the tree we got from the distance matrix method is equally parsimonious (simple) as the far right tree above. By that I mean the two trees both explain the data and we cannot say which one is more likely.