Adequacy of Numerical Taxonomic Methods: Why Not be a Pheneticist?

Abstract

A comparative study was conducted of the adequacy of phenetic and phylogenetic proce- dures, based on simulation experiments. Phenetic clustering methods examined included single linkage, complete linkage, average linkage, centroid sorting, median or Gower's method, Ward's method, Lance- Williams flexible BETA, and McQuitty's similarity analysis. Squared euclidean distance, product moment correlation, and cosine coefficient were used as (dis)similarity criteria, calculated both on standardized and non-standardized data. The Hennig86 and Wagner78 programs were used to calculate most parsimonious trees. The relative efficiency of these numerical procedures was evaluated using data matrices simulated under a large variety of evolutionary conditions. The efficiency was measured by the consensus of the true trees with the estimated ones, using Colless' consensus fork index (CFI). McQuitty's similarity analysis and the average linkage method based on cosine- or product moment correlation matrices for unstandardized characters were found to perform consistently better than the other phenetic clustering procedures and maximum parsimony. However, once again it was shown that none of these methods was very accurate. The majority of published phylogenies should therefore only be considered best approximations of the true tree.