Character Removal as a Means for Assessing Stability of Clades

The stability of each clade resolved by a data set can be assessed as the minimum number of characters that, when removed, cause resolution of the clade to be lost; a clade is regarded as having been lost when it does occur in the strict consensus tree. The clade stability index (CSI) is the ratio of this minimum number of characters to the number of informative characters in the data set. The CSI of a clade can range from 0 (absence from the consensus tree of the complete data set) to 1 (all informative characters must be removed for the clade to fail to be resolved). Minimum character removal scores are discoverable by a procedure known as successive character removal, in which separate cladistic analyses are conducted of all possible data sets derived by the removal of individual characters and character combinations of successively increasing number.