TAXONOMIC PRINCIPLES ^l 



of a group formerly supposed to be a natural (monophyletic) one as an 

 argument against the possibility of constructing a natural system is 

 nothing more nor less than to use the conclusion of phylogeny to dis- 

 prove phylogeny. 



The fallacy of the "fundamental" character 



Most workers today are aware that any ultimate system of 

 classification must be based upon the available data from all fields. 

 To assemble these data is difficult enough, but to assess their phyletic 

 significance often appears impossible. This is particularly true with 

 respect to morphological features (as opposed to chromosomal or 

 genetic data). For example, what genetic (or phylogenetic) signif- 

 icance does an inferior ovary versus a superior ovary have? How does 

 one evaluate the genetic significance of separate carpels as opposed 

 to fused carpels? Of course the answer is sometimes obvious when one 

 is considering the mere presence or absence of a given character 

 (other characters being similar), but when two taxa are separated by 

 a combination of morphological features, all of which vary, both 

 quantitatively and qualitatively, there is no simple solution. 



Because of the complexities involved, many workers set 

 arbitrarily certain "fundamental" or technical characters to mark 

 given groups. Consider the largest angiosperm family, the Compositae, 

 with over 30,000 species. All of the species are more or less ahke 

 m that most contain an involucrate head, four or five united petals, a 

 modified calyx-like structure (the pappus), an inferior ovary and two 

 carpels, a single style with two branches, and so on. In spite of 

 the extraordinary similarity of all of the species in this family, most 

 workers have grouped the species into twelve or thirteen tribes. The 

 tribal groupings are mostly natural, but occasionally certain taxa are 

 misplaced as to tribe, mainly because of the too rigid adherence to the 

 so-called "fundamental" features used to delimit the tribes initially. 

 For example, the genus Hymenopappus had long been placed in the 

 tribe Helenieae because of the absence of chaff. However, more recent 

 investigation has shown this genus to be unnaturally placed in the 

 Helenieae, since its most closely related taxon, Leucampyx, an 

 obvious prototype for the chaffless Hymenopappus, is apparently cor- 

 rectly placed in the tribe Anthemideae. The presence or absence of 

 chaff in this case appeared to be sufficiently "fundamental" to some 

 workers to separate two very closely related taxa, not only into 

 separate genera, but even into separate tribes. However, Turner 

 (1956), on the basis of total data, united the groups in a single genus 



