Contribución al conocimiento de la vegetación de la Sierra de Velasco en La Rioja, Argentina

Background and aims: The vascular flora of Sierra de Velasco from La Rioja Province (northwestern Argentina), belonging to the extra-Andean range Sierras Pampeanas, has not been systematically studied. The goal of this work was to describe the plant diversity of the Sierra de Velasco along its altitudinal gradient (1500-4300 m). M&M: Plant collections from 2021 to 2024 in the Costa Riojana zone of the Sierra de Velasco, were carried out. Specimens were processed and determined, and then deposited in the UNCAT herbarium and at the Centro Regional de Investigaciones y Transferencia Tecnológica de La Rioja. Results: Two hundred and sixty-nine species grouped in 199 genera and 81 families were recorded. Asteraceae had the greatest richness of species, followed by Fabaceae, Cactaceae, Solanaceae, Poaceae, and Verbenaceae. Forty-two taxa were recorded for the first time for La Rioja Province. Species of the Monte, Chaco, Yungas, Comechingones, Puna, and High Andes phytogeographic regions are distributed in altitudinal ranges comparable with neighboring mountains. Species that inhabit the highlands of the Sierra de Velasco suggest a biogeographic connection to the Puna Húmeda. Conclusions: This first systematic record of the vegetation of the Sierra de Velasco allows understanding its biogeographic relationships and provides key data for its conservation in face of climate change and environmental degradation.