Figure 1.

An example of two applications of the Z-rule, which underpins the Z-closure supernetwork method, where two partial splits displayed in the input trees (A) are extended to complete splits as shown in (B) and (C). The bold lines that form the 'Z' shape indicate that the intersection of the taxon sets is non-empty, eg in (B) {C,D}∩ {D,M} = {D}, {D,M}∩ {M,P,T} = {M}, {M,P,T}∩ {O,P,T} = {P,T}, but {C,D}∩ {O,P,T} = ∅ so the Z-rule can be applied.

Holland et al. BMC Evolutionary Biology 2008 8:202   doi:10.1186/1471-2148-8-202
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