Morphological Variation and Species Recognition in the Neotropical Taxon Vernonia arborescens (Compositae)

Abstract

Extensive morphological variation and a wide geographical range have led to difficulties in the taxonomy of Central American and West Indian species of Vernonia. Vernonia canescens and its relatives in Central and South America, and V. arborescens and V. divaricata of the West Indies, were similar appearing species whose taxonomic boundaries were poorly defined. These taxa had been distin- guished primarily on the basis of leaf size, shape, and characteristics of the indument. Detailed comparison of vegetative and reproductive characters within and between populations of these taxa from Central America and the West Indies revealed ex- tensive morphological variation. No characters were found that can be reliably used to separate taxa in this group. Other similar appearing taxa from northern South America, such as V. volubilis, were also found to be identical. Consequently, one highly polymorphic species, Vernonia arborescens, is recognized from the West Indies and Central and South America.