Dicoma

Abstract: Summary Ortiz, S.: Reinstatement of the genus Macledium Cass. (Asteraceae, Mutisieae): morphological and phylogenetic arguments.- Taxon 50: 733-744. 2001.- ISSN 0040- 0262. Studies of the genus Dicoma Cass. (Asteraceae, tribe Mutisieae) indicate that this taxon as currently defined is paraphyletic, and in fact comprises three groups showing marked morphological and anatomical differences. One of these groups is differentiated from Dicoma s.str. by a large number of characters relating to morphology and anatomy of phyllaries, corolla, anthers, style, cypsela, and testa. It is proposed that these species should be considered as a separate genus, for which the name Macledium Cass. has nomenclatural priority. A brief nomenclatural synopsis is presented, including synonyms and nomen- clatural types for each taxon in this genus of 20 species. type species D. tomentosa Cass. The first proposed subdivision of the genus was that of Lessing (1830), who divided it into three unnamed (merely numbered) sections containing six species. Subsequently, Lessing (1832) raised these informal sections to the rank of subgenus, with the following denominations: Leucophyton Less., Rhigiothamnus Less., and Macledium (Cass.) Less., this latter based on the genus that Cassini (1825) had described for the species Macledium burmanni Cass. Candolle (1838) recognised 10 species within Dicoma grouped into five sections: Eudicoma DC., Steirocoma DC., Rhigiothamnus (Less.) DC., Macledium (Cass.) DC. and Pterocoma DC. Harvey (1865) recognized 11 species of Dicoma in South Africa grouped into five sections almost coinciding with those of Candolle (1838), but omitting section Eudicoma and including the new section Psilocoma Harv. Subsequently, Hoffmann (1893) recognised 30 species grouped into eight sections, including the five sections of Candolle (1838), as well as Psilocoma, Hochstetteria (DC.) O. Hoffm., and Brachyachaenium (Baker) O. Hoffm., these latter two names based on two genera described by Candolle (1838) and Baker (1890) for Hochstetteria schimperi DC. and Brachyachaenium incanum Baker. Wilson (1923) recognised 34 species of Dicoma, which he grouped into three sections differentiated exclusively by pappus type, namely Dimorphae, Barbellatae, and Plumosae. Since the publication of Wilson's monograph, many new species have been described and the genus is currently considered to contain between 50 and 65 species (Bremer, 1994; Ortiz & al., 1998) ranging from annual or perennial herbs to shrubs or small trees, and distributed largely in tropical Africa, South Africa, and