Redécouverte de Gyalidea asteriscus (Ascomycota, Gomphillaceae) à Fournès (France) : une espèce très rare retrouvée après plus de cinquante ans dans sa localité historique française

The Star lichen, Gyalidea asteriscus (Anzi) Aptroot & Lücking, is a rare species restricted to calcareous or loess soils. It is confined to relict and threatened xerothermic (or steppe) habitats. First recorded in France by Clauzade and Roux in 1972 in the Fournès Badlands, it was considered extinct following the establishment of a brickworks on this site in 1978. Its rediscovery in 2025, with the identification of eight populations, confirms its persistence in this locality. Morphological and anatomical analysis of the specimens establishes these specimens as G. asteriscus subsp. asteriscus. Compilation of worldwide data from GBIF, iNaturalist and literature highlights a fragmented distribution across four main regions: Europe, North America, South America (Peru), and Asia (northern China, Kyrgyzstan, Pakistan and Russia). However, most of these records are based on historical data and likely no longer reflect the current distribution of the species. The absence of molecular data also leaves open the question of whether these records represent a single species or a complex. In central Europe, populations can be locally abundant, but their distribution is fragmented and confined to small areas. In France, three confirmed sites are currently known: Fournès (Gard), Hautes-Pyrénées and Maurienne (Savoie). Recent surveys underline the patrimonial value of the Fournès Badlands, which also host other rare lichens (Acarospora nodulosa, Diploschistes diacapsis) and noteworthy vascular flora (Stipellula parviflora, Strigosella africana). Three lichenized fungi are also newly reported for the Gard department: Caloplaca raesaenenii, Diplotomma murorum and Placidium tenellum. The combination of threats such as active soil erosion in the locality, amplified by human activities (soil extraction, agriculture and climate change), support the inclusion of G. asteriscus on the French Red List of lichens and the need for targeted conservation measures for theses fragile areas.