A new species of Grausa (Loasaceae: Cornales) from the arid Andes of Northern Chile and Western Argentina

Here we describe Grausa lutea spec. nov., from the Andes of the Coquimbo Region, Chile and San Juan Province, Argentina. We carried out both molecular phylogenetic analyses and morphological studies on this taxon. Molecular analyses were carried out on a concatenated matrix including the plastid regions matK, rps16, trnL-trnF, trnS-trnG, using both Maximum Likelihood and Bayesian Inference approaches, based on a sampling of 90 species of mostly “South Andean Loasas”. These recover Grausa as small but a well-supported clade, sister to a significantly larger clade that includes Pinnasa+(Scyphanthus+Caiophora). Grausa lutea is retrieved in a small clade that includes the two other acaulescent, high-Andean species of the genus: G. acaulis and G. lateritia. These three species in turn are sister to G. gayana. Morphologically Grausa lutea can be distinguished from its closest relatives by its bright yellow corolla (unique in Grausa) and nectar scales and its usually nodding flowers with a spreading corolla. The species is restricted to rocky slopes above 3000 m in arid high-Andean habitats, representing a significant northward extension of the ecological and geographic range of Grausa. Based on its very limited geographical and ecological range, and ongoing aridification in the region, G. lutea is preliminarily assessed as Endangered (EN) under IUCN criteria.