An Analysis of the Characters and Relationships of the Tribes Eupatorieae and Vernonieae (Asteraceae)

Abstract

The Eupatorieae and Vernonieae differ in pubescence, leaf insertion, leaf shape and venation, corolla lobe form, anther bases, anther pubescence, endothecial cells, pollen grains, style branches, achene walls, and pappus. The Eupatorieae are related to the Heliantheae in the subfamily Asteroideae, and the Vernonieae are placed close to the Liabeae and Mutisieae in the subfamily Cichorioideae. The family Asteraceae has presented continuing problems for taxonomists as a result of its size and its recurring combinations of superficial characters. Efforts to understand the limits of the subfamilies and tribes have suffered particularly. Where recent detailed studies have been undertaken they rarely extend beyond the limits of a single tribe. The critical anatomical tribal distinctions of Cassini (1813) are usually acknowledged but are rarely actually observed. Taxonomists tend to rely for identifications and judgments on the more easily observed characters such as those emphasized by Bentham (1873). Evidently few workers recognize that characters that may serve well in identification are not necessarily a reliable guide to phylogeny. These approaches have perpetuated traditional concepts that contain many errors. An example is the apparent presumption of close relationship between the tribes Eupatorieae and Vernonieae. The Eupatorieae and Vernonieae bear superficial resemblance in head form and flower color, and they have been placed together in most treatments including those of Cassini (1827) and Bentham (1873). Members of these tribes are often confused in preliminary identifications by nonspecialists, and a few errors by specialists are known. The two tribes have most of their diversity in the Neotropics, a region most inadequately treated in early European studies such as that of Bentham. Nevertheless, in the last 100 years the status of the tribes seems to have entered the realm of conventional wisdom with most workers unaware that there is any problem. Numerous characters are now available which show that the Eupatorieae and Vernonieae are not closely related, but these characters have never been effectively summarized. Many of the characters are also potentially useful in identification. The present survey is based primarily upon my own observations, though precedents are cited where these are known. As a point of reference I use Vernoniafuertesii (Urban) H. Robinson of Hispaniola, which has the distinction of having been originally described as a Eupatorium. 1 Botany, Smithsonian Institution, Washington DC 20560.