Characters, Computers, and Cladograms: A Review of the Berkeley Cladistics Workshop

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Abstract
A workshop on cladistic methods was held in Berkeley, 23-28 Mar 1981. It was unusual in that it emphasized analysis of data sets submitted by the participants. This focused attention on the construction of data sets and the differences among computer algorithms rather than on issues of classification or historical biogeography. Like any approach to phylogeny reconstruction, cladistic methods depend heavily on choice of characters and character states, as well as determination of evolutionary polarity and transformation series, and implicit or explicit character weighting. If the group being analyzed is not monophyletic or if it includes hybrids the cladistic relationships of the taxa may be misinterpreted. Minor changes in the choice of characters or the choice of taxa often produced major differences in cladograms. Such problems may be magnified by computer analyses. Different algorithms produce different results because they are based on different assumptions about the likelihood of character state changes. Despite these problems, the great strength of cladistic methods is that they force careful consideration of the nature and distribution of taxonomic characters and in doing so provide us with our best estimates of phylogenetic history.