LAUSR

Festuca is a genus of the Poaceae family with about 140 species in South America. Little information is available about Festuca species growing in the Eastern Sierras Pampeanas in Argentina, a region with a significant degree of endemism. The taxonomic delimitation of some species of this region is imprecise. One such taxon is Festuca lilloi, which has not only been recognized as a native species of the Peruvian Andes or endemic to the Western Sierras Pampeanas (northern Argentina), but also as a dominant floristic element in the Eastern Sierras Pampeanas (central Argentina). In spite of its ubiquity, there is very little information on variation in its morphology, anatomy and ecology across the Sierras Pampeanas and in adjacent areas. Recent fieldwork has resulted in the finding of a new species of Festuca that was erroneously assigned to Festuca lilloi. Morphological and anatomical differences between F. lilloi and the close species are evaluated, as are the species’ ecological preferences. The delimitation of the new species, named here as Festuca giraldoi, follows the morphological species concept. A detailed description of the morphology, leaf anatomy and epidermal micromorphology (leaf and lemma) is provided for the new species.