Effect of Changes in Character-Sets Upon Within-Group Phenetic Distance

Abstract

Gilmartin, A. J. (Department of Botany, Washington State University, Pullman, Wa. 99163) 1976. Effect of changes in character-sets upon within-group phenetic distance. Syst. Zool. 25:129–136.—Tests were made to ascertain the effect upon computed phenetic distance values of using different character-sets. Random selection of various sized subsets of the total character-list were made in order to simulate the differences which occur due to mixed, missing data. The phenetic distances were computed from sub-sets of characters which were selected from lists of characters for bromels, milkweeds, and legumes. Distances are treated as new variates. Means and standard deviations were found for the OTU × OTU distance matrices computed with less than and more than 50% of the total character-set. While significant differences were revealed between means computed with character-sets of 13 and 30% of the total, matrical summary statistics did not differ significantly when the number of characters represented 50% or more of the total set. Some evolutionary connotations are discussed. Tests showed little evidence of heterogeneity of variance. The results support the use of summary statistics of phenetic distance matrices to express intra-group variation, but with the caution that the biologist should be aware of the actual number of characters being used to compute the phenetic distances.