A Taxonomic Revision of Heterosperma (Asteraceae: Coreopsideae)
The New World genus Heterosperma Cav. is circumscribed to include 11 species: H. achaetum S. F. Blake, H. diversifolium Kunth, H. ferreyrii H. Rob., H. mexicanum (A. Gray ex S. Watson) Lizarazu & S. E. Freire, H. nanum (Nutt.) Sherff, H. ovale S. F. Blake, H. ovatifolium Cav., H. pinnatum Cav., H. spathulatum S. F. Blake, H. tenuisectum (Griseb.) Cabrera, and H. trilobum S. F. Blake. Heterosperma is described as having a usually herbaceous habit, pinnatisect or entire leaves, radiate capitula, and heteromorphic cypselae. The following taxa are newly synonymized: Coreopsis L. sect. Anathysana S. F. Blake with Heterosperma; H. maritimum Kunth var. hirsuta Hieron. with H. ovatifolium; and H. maritimum var. latifolia Hieron. with H. spathulatum. Lectotypes are here designated for H. maritimum var. hirsuta, H. pinnatum, H. tagetinum A. Gray, H. spathulatum, and H. maritimum var. latifolia. A key to the species of the genus is provided, as well as morphological descriptions, illustrations, and distribution maps. A detailed morphological study of trichomes and pappus is also presented.