Juan S. Álvarez-Aspra, Eva Barreno The lichen Ricasolia virens has a wide geographical distribution in Europe, and is considered (Red Lists, IUCN) one of the best bioindicators of mature forests, with ecological continuity, without significant anthropogenic impacts. However, the biology and ecology of its thalli and populations have been scarcely studied. Its importance as a sensitive bio-indicator makes its knowledge an important tool to establish which are the best-conserved and structured forest areas, on which to focus the management and to monitor its possible evolution due to negative impacts. It also provides an accurate scientific basis for effective conservation actions and for assessing the endangered status (Red Lists). In this work, an original niche study on the populations of R. virens in a Special Area of Conservation, the Sierra del Sueve mountains (Natura 2000-ZEC ES1200043, Asturias, Spain) was carried out by means of bioinformatics analyses, with the aim of generating a predictive model to assess the distribution of the populations of this species in and its potential application to the biomonitoring of woodlands. Based on thalli, in populations known since 2008, this study has been able to generate a predictive model to assess the presence of R. virens, which has fourfold improved the quantitative estimation of the populations, from the initial 13 up to 60 phorophytes. The study also extends the types of trees previously known to host this lichen in this mountain range. In addition, it has been found that, despite being labelled as a sciophytic taxon, R. virens seem to behave like a photophilous species. The Sierra del Sueve could be interpreted as “a refuge area” for this lichen in Europe. Nevertheless, we also found some thalli with visible signs of damage in phorophytes close to trails, forest tracks and zones frequented by animals, which indicates the presence of disturbances that may threaten their long-term survival in these forests. Project: PROMETEO/2021/005 (GVA to EB).