Methods for showing Distinctness and aiding Identification of Critical Groups in Taxonomy and Ecology

Abstract

IN recent studies of critical groups in the genus Satyrium Sw. (Orchidaceae), specimens have been grouped on the basis of numerically expressed properties, using the homogeneity function¹ for pair-comparisons, followed by group average linkage clustering². This results in a dendrogram such as that shown by the solid lines in Fig. 1. When restricted to pair-comparisons (as is necessary for samples³), the heterogeneity function for two-state and quantitative data reduces to a modulus generally similar to those of Cain and Harrison⁴, Colless⁵ and others. Usually only the links selected by the clustering system are shown in the dendrogram. For checking on the intermediate nature of some members in the present work, it was found helpful to include values for some of the other relationships in the closing stages of each study. For example, the dashed line in Fig. 1 helps to show that group B is nearly intermediate between groups A and C.