Bromus catharticus in South America (Poaceae: Bromeae)

Abstract

A new combination, Bromus catharticus var. rupestris, is made. Based on morphological evidence this taxon seems best recognized at the varietal level. Detailed illustrations of B. catharticus var. rupestris and B. catharticus var. catharticus are included along with morphological descriptions, distributions, and representative specimens. RESUMEN. Se realiza una nueva combinaci6n, Bromus catharticus var. rupestris. Sobre la base de las evidencias morfol6gicas, parece mejor reconocer este taxon a nivel de variedad. Se incluyen illustraciones detalladas de B. catharticus var. rupestris y B. catharticus var. catharticus junto con descripciones morfol6gicas, distribuciones y especfmenes representativos. Bromus L. comprises approximately 150 species found mainly in the temperate regions of both hemispheres (Clayton & Renvoize, 1986). The genus has been divided into five to seven groups (Stebbins, 1981; Tsvelev, 1976), depending upon the recognition of Anisantha C. Koch, Boissiera Steudel, Bromopsis Fourreau, Ceratochloa P. Beauvois, and Nevskiella Krecz & Vvedensky as separate genera. In a recent treatment of Bromus in the United States and Canada, Pavlick (1995) recognized five sections: Bromopsis, Bromus, Ceratochloa, Genea, and Neobromus. In North and South America, Bromus sect. Ceratochloa consists of approximately 18 species of which B. catharticus Vahl is a member (Matthei, 1986; Nicora, 1978; Pavlick, 1995; Pillay & Hilu, 1995; Soderstrom & Beaman, 1968; Tovar, 1993; Zuloaga et al., 1994). This section is entirely native to the New World and contains an extensive polyploid complex, base of x = 7. All taxa thus far examined are either hexaploid (2n = 42), octoploid (2n = 56), or duodecaploid (2n = 84) (Armstrong, 1991; Pavlick, 1995; Stebbins, 1956, 1981; Stebbins & Tobgy, 1944). Bromus catharticus and immediate relatives are all hexaploid (Naranjo, 1992). The Bromus catharticus complex presently contains six taxa (Planchuelo, 1991; this paper): B. bonariensis Parodi & J. A. Camara, B. brevis Nees ex Steudel subsp. brevis, B. brevis subsp. festucarioides Covas & Millot, B. catharticus, B. parodii Covas & Itria, and B. striatus Hitchcock [= B. catharticus var. striatus (Hitchcock) Pinto]. We choose to recognize B. catharticus, as proposed by PintoEscobar (1976), as the true name for rescue grass, rather than that proposed earlier by Raven (1960) as B. willdenowii Kunth. The Andean species, B. unioloides Kunth, and B. willdenowii are treated here as taxonomic synoyms of the older, B. cathar-