The Phenetic Relationships of the Butterflies I. Adult Taxonomy and the Nonspecificity Hypothesis

Abstract

The relationships of adult butterflies were evaluated using the techniques of numerical taxonomy and various sets of characters. Using a total of 196 characters of the external and internal anatomy produced phenograms quite similar to the one arrived at by classical taxonomic techniques. There were, however, significant differences (e.g., relatively low of the Papilionidae and Pieridae). Relationships based on most subsets of characters showed a family resemblance to one another and to the classical relationships. Relationships based on 96 internal and 100 external characters were compared by a randomization test. When evaluated by correlation coefficients the internal and external relationships were significantly different. When evaluated by distances they were not. Our results in general seem to support a weak version of the nonspecificity hypothesis-analysis of different large samples of characters ordinarily will yield positively correlated but non-identical patterns of relationship. This study has led to an appraisal of ideas of general classification and the utility of numerical taxonomy. Theoretical considerations make it seem unlikely that the idea of similarity has any validity. In any case it is clear that overall cannot be dealt with operationally. All classifications are inherently special, and no one special classification is any more or less correct than any other. It is suggested that numerical taxonomy is a more sophisticated tool than is required for doing most routine taxonomic jobs. Numerical taxonomy, however, can be used in those situations where refined answers seem to be desirable, either where economic problems are involved or where light can be shed on general problems of population biology. In recent years the development of numerical taxonomy (Sokal and Sneath, 1963) has given population biologists new tools for studying the phenetic relationships among groups of organisms. These developments have been part of a general trend toward a more operational approach to population biology (Ehrlich and Holm, 1962), and have led to a searching evaluation of taxonomic principles and procedures (e.g., Michener, 1963; Ehrlich, 1964; Heywood and McNeill, 1964; Sokal and Michener, 1967). Some of the more interesting questions raised in connection with the numerical taxonomic revolution have concerned special versus general classifications and the relevance of taxonomies based on limited sets of characters. Although the matter has been widely discussed, only two substantial pieces of published work have been designed specifically to investigate this problem, that of Rohlf (1963) who compared adult and larval classifications in Aedes mosquitoes and that of Michener and Sokal (1966) who compared classifications of the Hoplitis complex of bees based on different sets of characters. The present paper summarizes a series of studies designed to evaluate special classifications of adult butterflies. Materials and methods.-Thirty-one species of butterflies (Papilionoidea) representing all five families and 17 of the 19 subfamilies (Ehrlich, 1958a) were chosen as OTU's for the study. Two additional OTU's representing two of the subfamilies of skippers (Hesperioidea) were included. These species and the numbers assigned to them were: PAPILIONIDAE: Papilioninae 1. Graphium philolaus Bdv. 2. Papilio glaucus L. 3. Papilio multicaudata Kirby 4. Battus philenor L. PAPILIONIDAE: Parnassiinae 5. Parnassius phoebus Fabr.