Habital variation in the Hawaiian Madiinae (Heliantheae) and its relevance to generic concepts in the Compositae

The Hawaiian Madiinae constitute a genetically cohesive and presumably monophyletic alliance of 28 species of extreme habital diversity which traditionally have been dispersed among four genera that are defined primarily by floral and foliar features. Dozens of natural and artificial hybrids between generic and habital categories have been produced. Cytogenetic data indicate that definition of genera according to habit would result in a number of fragmentary groups, each heterogeneous with respect to chromosome number and/or structure. Moreover, in a number of instances species of known cytogenetic identity would be placed in two or more different genera. Disposition of the 28 species in three traditionally recognized genera is recommended. These are Dubautia sensu lato, Argyroxiphium, and Wilkesia.