Figure 3

NNI. A single NNI on and $\hat{\mathcal{G}}$. On the left e_i and $e_i^{\prime }$ (for i = 0, ... , 4) denote edges in and its NNI-neighbor ${\mathcal{G}}^{\prime }$, respectively. On the right each node a _i denote the labeling of edges in $\hat{\mathcal{G}}$. Notation ${ā}_i$ denote the lca-mapping of complementary subtrees, for instance, ${ā}_3=a_1+a_2+a_4$, etc. For brevity, we omit each subtree T _i attached to w _i in the left diagram.