Eriocomavaldesii, a new species from México (Poaceae, Stipeae)

Abstract Eriocomavaldesiisp. nov., is described and illustrated. The new species was found growing on calcareous rocky slopes and hillsides between 1700–2721 m in Coahuila, Nuevo León, San Luis Potosí, and Tamaulipas. The new species is morphologically similar to Eriocomalobata but differs in having ligules (2–) 4.5–8.5 mm long with acute to narrowly acute and lacerate apices and florets with a sharp-pointed callus. In addition, we include a key to the species of Eriocoma in northeastern México.

Eriocoma Nutt., recently resurrected to replace Achnatherum P. Beauv. for most of the American species, consists of 27 species in North America (Canada, México, and USA), and is characterized by having a maize-like lemma epidermal pattern along with the same features mentioned above for the tribe (Romaschenko et al. 2012(Romaschenko et al. , 2014Peterson et al. 2019). Within México, 7-11 species of Eriocoma have been reported (Espejo Serna et al. 2000;Dávila et al. 2018;Sánchez-Ken 2018). The remaining six species of Achnatherum in México were placed in Pseudoeriocoma Romasch., P.M. Peterson & Soreng, and these all have woody, sometimes scandent bamboo-like culms with ramified branching at the middle and upper nodes (Peterson et al. 2019).

Eriocoma valdesii
Distribution. The new species is known from the Municipio de Bustamante in Tamaulipas, the Municipio Catorce in San Luis Potosí, the Municipio de Saltillo in Coahuila, and the Municipios Galeana and Santa Catarina in Nuevo León.
Conservation status. The species is rare in México, but with more collecting it probably will be found in the adjacent state of Zacatecas.
Etymology. The specific epithet honors Jesus Valdés Reyna (1948-), a renowned Mexican agrostologist, friend, and colleague who PMP, RJS, and KR have worked with for more than 35 years.
In our preliminary molecular DNA sequence analysis of most American species of Eriocoma there is a strongly-supported E. lobata I clade (including the type) found allied with E. coronata (Thurb.) Romasch., E. parishii (Vasey) Romasch., and E. perplexa (Valdés Reyna et al. 2013). In another portion of our tree a strongly-supported clade of five accessions of E. valdesii (including Peterson, Romaschenko & Valdés Reyna 24469, the type collection) forms a trichotomy with two other strongly-supported clades containing three accessions of E. alta (including the type) and seven accessions of E. lobata II (Valdés Reyna et al. 2013