Do gypsophile lichens exist? Analysis of the affinity for the gypsum substrate of lichen species from Spain

Gypsum soils, despite physico-chemical constraints, harbor a unique biota composed of specialist (gypsophiles) and stress-tolerant non-specialist species (gypsovags). Gypsophily has been addressed in plants, although is important to ask whether lichen communities also contain gypsophile species. Therefore, our main aim is the analysis of the affinity of lichens for the gypsum substrate in Spain. Affinity was estimated using two methods: a “geological method”, overlapping lichen occurrence data on a geological map of Spain; and a “biological method”, overlapping the occurrences on a map constructed with the distribution of plant gypsophiles. To assess the accuracy of both methods, we compared them with a literature review. Lichen occurrence data was obtained from GBIF. The biological method was the most accurate as it showed similar percentages to the literature review. The affinity for gypsum substrate has been effectively demonstrated by the employment of these methods, probing the existence of a group of lichens considered gypsophiles. Twenty lichen species are considered gypsophiles, 7 strict and 13 preferential (ca. 40% of 50 taxa analyzed), and 30 gypsovags. This approximation can apply to the study of the affinity for the substrate for other organisms/substrates, and for characterizing geological units when detailed geological maps are not available.