Table 2. Summary statistics based on the tree topology (topo set).

Notation	Description
colless	Sum for each internal node of the absolute difference between the number of leaves on the left side and the number of leaves on the right side [47]
sackin	Sum for each leaf of the number of internal nodes between the leaf and the root [48]
WD_ratio	Ratio of the maximal width (W) over the maximal depth (D), where the depth of a node characterizes the number of branches that lies between it and the root, and the width wd of a tree at a depth level d is the number of nodes that have the same depth d [49]
Δw	Maximal difference in width $\Delta w={\text{max}}_{d=0}^{D-1}\left(\right|w_d-w_{d+1}\left|\right)$ [49]
max_ladder	Maximal number of internal nodes in a ladder which is a chain of connected internal nodes each linked to a single leaf, divided by the number of leaves [49]
IL_nodes	Proportion of internal nodes In Ladders [49]
staircaseness_1	Proportion of imbalanced internal nodes that have different numbers of leaves between the left and the right side [49]
staircaseness_2	Mean ratio of the minimal number of leaves on a side over the maximal number of leaves on a side, for each internal node [49, 50]