1 Mediterranean Botany 43, e77925, 2022 Sierra Nevada (Spain), the southernmost European locality for the polar-alpine Umbilicaria aprina and U. virginis Leopoldo G. Sancho 1 , Ana Aramburu 1 , Ana Pintado 1 , Manuel Casares 2 , José Raggio 1 & David Sánchez-Pescador 1 Received: 14 September 2021 /Accepted: 21 January 2022 / Published online: 26 April 2022 Abstract: Two strict polar-alpine Umbilicaria species (U. aprina and U. virginis) are reported growing together in Los Peñones de San Francisco. Other localities known on the highest summits of the Alps and Pyrenees are considered. We discussed the meaning of these isolated populations as glacial relicts. How to cite: Sancho, L.G., Aramburu, A., Pintado, A., Casares, M., Raggio, J. & Sánchez-Pescador, D. 2022. Sierra Nevada (Spain), the southernmost European locality for the polar-alpine Umbilicaria aprina and U. virginis. Mediterr. Bot. 43, e77925. https://doi.org/mbot.77925 1 Department of Pharmacology, Pharmacognosy and Botany, Faculty of Pharmacy, Complutense University. E-28040 Madrid, Spain. Email: sancholg@ucm.es 2 Botany Department, University of Granada. E-18071 Granada, Spain. Mediterranean Botany ISSNe 2603-9109 https://doi.org/mbot.77925 SHORT NOTES Umbilicaria aprina and U. virginis could be considered as extremist due to their distribution, with a clear preference for the coldest areas of the world. U. aprina was described frstly in the high mountains of Ethiopia (Nylander, 1860). Later it was found in Scandinavia (Santesson, 1993), the Alps (Frey, 1933; Hasenhüttl & Poelt, 1978; Codogno, 1995; Hafellner & Türk, 2001), the Tatra Mountains (Krzewicka & Osyczka, 2002; Lisická, 2005) and Central Asia (Poelt, 1977; Wei & Jiang, 1993; Kudratov, 2004). In the Arctic it is known from Greenland (Ryvarden, 1968; Hansen, 2003), Svalbard Islands (Øvstedal et al., 2009) and to Baffn Island (Hale, 1954) and Iceland (Kristinsson, 1974). Recently U. aprina has been reported from the French Pyrenees by Hestmark (Hestmark, 2015), in what was the southernmost European locality for this species until now. This author highlights the remarkable inverse correlation between latitude and altitude for this species, from a minimum of c. 1100 m asl in southern Norway, to c. 2100 m asl in Poland, to 3100 m asl in the Alps and the Pyrenees, and to 4400 m asl in equatorial Africa and South America (Crespo & Sancho, 1982; Krog & Swinscow, 1986; Hestmark, 2009). Therefore, Los Peñones de San Francisco (Sierra Nevada, Spain), where both U. aprina and U.virginis species coexist at an altitude of only 2500 m asl and a latitude of 37ºN, is a particularly unique spot (Figure 1a). However, it is in Antarctica where U. aprina reaches its maximum abundance and biomass (Filson, 1975; Øvstedal & Lewis-Smith, 2001; Sancho et al., 2003). This is arguably the most abundant of all macrolichens in many localities on the Antarctic continent. It can be found from the coast (Seppelt et al., 2010) to the inland, including the slopes of the inhospitable McMurdo Dry Valleys (Green et al., 2007; Cannone & Seppelt, 2008). In some areas, extraordinary thalli, easily exceeding 10 cm in diameter, can be considered an example of gigantism, a term frequently associated with some Antarctic organisms (Øvstedal & Lewis Smith, 2001). Also, morphological variations in colour and thallus anatomy related to environmental gradients have been discovered and studied (Sancho et al., 2003). Sexual reproduction of this species has never been found in Antarctica so far. In Los Peñones de San Francisco U. aprina does not exhibit apothecia either and thalli are much smaller reaching a maximum of 2.5 cm in diameter. It grows on west-south-west facing rock walls, occupying small ledges, not far from the abundant populations of U. virginis, but without mixing with it. U. aprina had not yet been reported in the checklist of Spanish lichens (Llimona & Hladun, 2001), nor in the very recent checklist of Sierra Nevada lichens (Gómez- Bolea et al., 2021). However, it is mentioned from the highest summit of Sierra Nevada (Mulhacén 3420 m asl) by Codogno (Codogno, 1995) who found it immixed with U. virginis in old herbarium samples. In contrast, Umbilicaria virginis is a well-known species from Los Peñones de San Francisco and the summits of Sierra Nevada (Werner, 1975; Casares & Llimona, 1982; Egea et al., 1982; Gómez-Bolea et al., 2021). In Los Peñones de San Francisco it is relatively frequent, colonising more or less vertical runoffs, with a clear preference for western or south-western aspects. Keywords: Lichens, Polar-alpine, Biogeography, Umbilicaria, Sierra Nevada.