THE SECTIONAL NOMENCLATURE OF EUPATORIUM (ASTERACEAE)

Abstract

The genus Eupatorium (Asteraceae) has traditionally been treated as one of the largest in the family, with some 800 recognized species. It was divided into sections by several authors, mostly in the nineteenth century, but the sectional names which gained general use (summarized by B. L. Robinson, 1918 and Barroso, 1950) were often not those with priority. In a recent series of papers (summarized by Robinson and King, 1977) R. M. King and H. Robinson have pointed out many artificialities in these older systems and proposed a reclassification of the tribe Eupatorieae, in which ca. 95% of the species have been moved out of Eupatorium s. lat. into other genera. In the course of that work the typification of the old generic names in the tribe was reviewed and completed, but the sections of Eupatorium, except those which have also been treated as genera, have never been typified. I list below all the sections of Eupatorium known to me (I know of no validly published subgenera in the genus) in order of their priority at this rank. About half of them have been typified, were originally monotypic, or were named for an included species and are therefore automatically typified under Article 22.4 of the Code; the rest are lectotypified here. For each type I also give the accepted name in Eupatorium and the name assigned by King and Robinson, if they are different. Several of these names have not been used since they were first published. Others have been widely used for large artificial groups of species, and it would be confusing to have to use them for small natural species groups, especially if they replace more familiar names which have been published more recently. Furthermore, recent authors disagree greatly about what generic concept to employ in the Eupatorieae. Comparing the work of different authors would be simpler if the subgeneric and sectional names of the lumpers matched the generic names of the splitters, and old unfamiliar sectional names prevent such a convenient arrangement of the nomenclature. For these reasons, in four cases where it is consistent with the protologue (sect. Luxuriantia, sect. Heterolepis, sect. Subimbricata and sect. Eximbricata) I have intentionally typified sections so as to place them permanently in synonymy. The rest of the types have been selected as species typical of each section as it was circumscribed in its protologue. The names published by Loudon and listed below require brief comment. The more inclusive of his infrageneric taxa are established at the rank of section by his statement (p. iv) that the larger genera are subdivided into sections and subsections. I have typified only his four sections, but there are also nine subsections which will have to be dealt with if this rank is ever used in Eupatorium. In addition to the taxa listed below, Baillon (1882) reduced many of the then-recognized genera of Eupatorieae to sectional status under Eupatorium. I know of nobody who has followed his broad concept of the genus; indeed, of the fifteen sections he proposed only one (Eupatorium sect. Mikania (Willd.) Baillon, typified by E. scandens L.) has had a valid name published in Eupatorium for its type species. Although these names nomenclaturally belong to Eupatorium, they apply to species not treated in this genus by any other author and I see no need to list them here. All of their basionyms have been typified already (King and Robinson, 1969).