Consensus trees • In MP or ML analyses, more than one best cladogram may be obtained. Consensus methods are a convenient means of summarizing these cladograms. • Consensus trees are derivative whereas most parsimonious/likelihood trees are fundamental. • Consensus analysis almost invariably produces a tree that would not be supported as parsimonious/likelihood by the original data, and in some cases may even contain components not found in any of the fundamental cladograms. Therefore, its use for phylogenetic inferences is questioned.
Consensus methods • They are several consensus methods: • Strict Consensus • Semi-strict Consensus • Majority-rule Consensus • Adam Consensus
The most conservative consensus method. • Strict consensus tree contains only those groups that occur in all rival cladograms. Strict Consensus Strict consensus tree
Also called ‘combinable components’. • Semi-strict consensus tree contains those groups that occur in all rival cladograms and also non-conflicting groups. Semi Strict Consensus Semi-strict consensus tree
Majority-Rule Consensus • Majority-rule consensus is normally set at the cut off value of 50%. Thus, the groups retained must appear in more than half of the fundamental cladograms. • Cut off value can be set higher, say 75%. • Majority-rule consensus tree may be preferable to strict consensus when many trees are being compared.
Majority-Rule Consensus 50% majority-rule consensus tree
Adam consensus tree is derived by relocating those taxa that occur in conflicting positions on different fundamental cladograms to the nearest node they have in common. • Adam tree therefore contains all the intersecting sets of taxa (nestings) common to all the fundamental cladograms. Adam Consensus Adam consensus tree