Figure 1

Tree-building process by the core set approach. Figure a shows the excluding process of sequences in the order of the largest deviation from additivity. Finally, the 21 sequences remained for the P-core set formed by the single substitution (solid circle). The first 27 sequences give the S-core set which MP makes a unique tree (solid triangle in Fig. b). The first 34 sequences give the T-core set tree formed by using both the min-max criterion and the condition of preserving the S-core set tree, though MP shows 300 topologies (solid diamond in Fig. b). The inclusion of the remaining 4 sequences gives rise to an explosion of topology (the solid squares in Fig. b). Figure c follows the W_i values of sequences to be inserted into the core set by using both the min-max criterion.