Mutation tree with the 18 important sites in []. The pairwise mutation order relations of the 18 sites were selected by the Edmonds’ minimal spanning tree algorithm. Directions of branches in the tree represent the mutation orders between the corresponding two sites. The sites of the tree are ordered according to mutation rates which are shown in the left side. DLEC1 has the highest mutation rate 0.864 and PABPC1 has the lowest mutation rate 0.122. The leave-one-out replication result with 58 leave-one-out mutation trees is also summarized in the figure. Each branch has a number which represents how many times the branch is found in the 58 leave-one-out replication. Numbers in the three nodes (DLEC1, DMXL1 and TOP1MT) represent how many times each node is found as root in the 58 leave-one-out replication. The figure was produced by the R software , RBGL R package , and Graphviz .