Nassella: Species diversity and distribution (Poaceae: Stipeae)
Mary E. Barkworth & María Amelia Torres
Longer version of a paper to be published in Taxon later in 2001Summary
Nassella sensu lato includes 116 species, making it one of the largest genera in the tribe. Argentina has the largest number of species, 72, with the greatest concentration being in the northwestern part of the country. Bolivia, Chile, and Uruguay have 26, 27, and 27 species, respectively. Other South American countries in which the genus is present are Brazil (18 species), Colombia (8 species), Ecuador (10 species), Paraguay (4 species), Peru (18 species), and Venezuela (2 species). Guatemala has 2 species, but Costa Rica only 1. Mexico has 8 native species, 5 of which also grow in the United States. One additional species grows in both the United States and Canada. Sixty species are known only from one country; one species, N. mexicana, grows in 8 countries. Several new distribution records are documented: N. caespitosa, N. elata, N. leptothera and N. punensis for Bolivia, N. pauciciliata and N. spegazzinii for Brazil, N. ancoraimensis for Ecuador, N. airoides, N. argentinensis, N. spegazzinii for Paraguay, and N. tucumana (= N. asperifolia) for Peru. Three new combinations are presented (blanked out here until formally published). Two recently transferred species, N. barrancaensis and N. brachycaheta, are excluded from the genus and N. asperifolia, N. bonariensis, and N. amthethystina are placed in synonymy. Tables summarizing the distribution of Nassella and its morphological variation are presented.
 This research was supported by the Utah Agricultural Experiment Station, Utah State University, Logan, Utah 84322-4810. Approved as journal paper no. 7311.
 Intermountain Herbarium, Utah State University, Logan, Utah 84322-5305, U.S.A.
 Departamento Científico de Plantas Vasculares, Museo de La Plata, 1900 La Plata, Argentina.