Fig. 2

Crossover operator. a Subtree swap. A subtree G₁[ x] (in red) is pruned from G₁ then regrafted to a random branch of G₂ after deleting from G₂ its leaves that also appear in G₁[ x] (shown in dotted lines). To obtain the second child, a similar operation is performed from G₂ to G₁b Subtree swap preserving reconciliation. Two subtrees G₁[ x] and G₂[ y], respectively from G₁ and G₂, such that \(\overline {G_{1}[\!x]}=\overline {G_{2}[\!y]}\) are swapped and the remaining leaves are corrected to conserve the same leafset as the parent