Example of a DTL reconciliation. (a) A gene tree G, represented with lost copies of the gene (∘), and a subdivided species tree S′. (b) A reconciliation α between G and S′. The reconciliation maps each node of G onto a sequence of nodes in S′, inducing evolutionary events. For instance, nodes w,d1 and u from G are mapped as follows: α(w) = [y], where α1(w) = y is an event; α(d1) = [x′,x,D], where α1(d1) = x′ is a event, α2(d1) = x is an event, and α3(d1) = D is a event; α(u) = [y′,x,C], where α1(u) = y′, α2(u) = x, and α3(u) = C are respectively a , an , and a event.