A revision of Smallanthus (Asteraceae, Millerieae), the "yacon" genus

Smallanthus (Asteraceae, Millerieae), the "yacon" genus, comprises 23 species ranging from southeastern United States to central Argentina, with the greatest diversity in Peru and Mexico. Species of Smallanthus are herbs, shrubs or small trees with tuberous roots, opposite, trinerved or triplinerved leaves, paleate receptacle, ray corollas externally hairy at the base, pappus lacking, and marginal cypselae partially embraced by the inner phyllaries of the involucre. As a result of this revision: Smallanthus araucariophilus and S. riograndesis are considered synonyms of S. macroscyphus; lectotypes are designated for nine names; and the geographical distribution of S. latisquamus, S. lundelli, S. riparius, and S. siegesbeckia is extended. A comprehensive key to the species and detailed descriptions, geographical distribution, phenology, illustrations and distribution maps are provided for all taxa.