In the most recent monograph of the genus Trifolium, Zohary and Heller circumscribe Trifolium polymorphum in a broad sense, describing the species as ocurring in Texas, Arkansas and Louisiana as well as southern Peru and Chile to the coastal areas of southern Brazil and Argentina. This broad distribution suggested that the species was actually a species complex composed of more than one species. A morphological study of the species complex revealed that several species can easily be circumscribed, and these morphologically distinct entities also have distinct geographical distributions. These include a northern Chilean-North American species, several others from western South America, as well as several from southern and southeastern South America.

Key words: Fabaceae, new species, North America, revision, South America, Trifolium polymorphum