Fig. 3

Illustration of treatment of ambiguous character states. Two nucleotide characters having ambiguities (top left) are represented by pairs of sets (top right). The column designated “X” is represented by upper and lower bounds on the set of rows with “T”, although it could instead be represented by the set with “A”. Similarly, “Y” is represented in terms of the rows with “C”. The result of disambiguation using only information from this pair is shown at the bottom, including the implied effect on the nucleotide character states