Initial Biometric Survey of Morphological Variation in the Cirsium Altissimum-C. Discolor Complex

Abstract

According to Benson (1962), pressed herbarium specimens furnish data . forming the basis for tentative conclusions and generate the stimulus for further study of questions which specimens may raise but do not answer." The present study is intended as an example of just this sort of thing-the detection of a taxonomic problem from a limited sample of standard, one-collection-persite, herbarium materials. In a way the study represents a mathematical game using morphological data to elucidate a taxonomic puzzle. The "tentative conclusion" that arises from this study is that the biologic relationships and taxonomy of plants generally considered to comprise Cirsium alttissimum (L.) Spreng. and C. discolor (Willd.) Spreng. are poorly understood and confused. Some "further study of the questions which [the] specimens" raised already has been undertaken and these supplementary studies, involving field observations and population samples, controlled pollination experiments, pollen fertility determinations, and cytology, support the contention that the problem suggested here is a real biologic problem and not just an artifact of herbarium specimen morphology. However, these supplementary data are incomplete, and it is premature to suggest an explanation for the taxonomic problem considered here. Nonetheless the present work and the supplementary data did suggest a working hypothesis needed for continuity. This tentative hypothesis is introgression. This is not to say that the present study supports this hypothesis; as a safeguard against such an interpretation nmention of the supplementary data and of introgression is held to a minimum. The bulk of this paper is devoted then only to the elaboration of a problem. The question follows, "Then why not just say there is a problem? Why go to such lengths presenting data and 'playing mathematical games' and all.... ?" To my mind one of the most important changes that plant taxonomy will undergo during the next few decades will be a gradual gain in "taxonomy, the scienee" and a corresponding loss in "taxonomy, the art." Taxonomy will gradually become more objective-a greater number of "things" that go into the makeup of taxonomy will be things that are repeatable and verifiable. Taxonomic data from observation and experiment will become increasingly quantitative. As numerical data from various sources become available statistics will receive more attention and will find a rightful place in taxonomy as it has in so