VARIATION WITHIN POPULATIONS AND CLASSIFICATION

Abstract

SummaryVariation was measured in samples of populations of species from four plant families including tropical, temperate and cosmopolitan taxa. Populations of species of Asclepiadaceae, Bromeliaceae, Leguminosae and Umbelliferae were sampled. Employing a simple application of numerical phenetics and tested character lists, estimates of within‐group overall variation were made. The coefficients of phenetic variation (CPV) are compared among the various groups. The groups considered are populations as well as taxa at several levels in the classification hierarchy, although in all cases, individuals sampled randomly from putative populations are the operational taxonomic units (OTUs). A small number of individuals is employed with a large number of characters. This application of numerical phenetics serves both alpha taxonomic and biosystematic goals and an OTU x OTU matrix of distance values is the basis for obtaining estimates of a population's variability. The phenetic distances between OTUs are the variates. Distinct trends of within‐group variation are consistent as they were revealed in the four families. Intrapopulational coefficient of phenetic variation for populations of the tropical family Bromeliaceae is estimated as nearly double that for the other three families. The intraspecific variation as portrayed by CPV in the Asclepiadaceae and Leguminosae is about half that for the tropical family, Bromeliaceae. As sampled a clear distinction is evidenced in the change in variation between various taxonomic ranks for the families. The difference in CPV between the intrapopulational and intraspecific levels for the Leguminosae and Bromeliaceae is nearly double the difference between these two ranks for the Asclepiadaceae. Results show that the method has descriptive and heuristic value for systematics.