Lecidea promixta Nyl.

This little-known lichen produces small black apothecia, usually considerably less than 1 mm in diameter, constricted at their bases, and with a slightly elevated persistent margin. Discs are rough on the surface when properly magnified, but still less than in the rare montane taxon L. haerjedalica. The latter differs in the presence of a purple pigment in the hypothecium, and in the shape of ascospores. In both of these taxa, the distinctly darkly delimited, unequally broad epihymenium with unevenly stratified granules of a pigment between the dark and thickened ends of the paraphyses is visible in section under the microscope (see Hertel 2009). The ascospores of L. promixta are narrowly elongate-ellipsoid and the thallus is usually reduced, nearly absent (Hertel 1995, 2009, Arup 2004).

Lecidea promixta is an oceanic, rather lowland species of acidic siliceous rocks. Most of its records come from northern Germany, the southern part of the Great Britain and southern Sweden (Hertel 1995, Westberg et al. 2021). Given its known ecology and distribution, it is possible that the only published Czech historical record from the Mt Kotel in the Krkonoše Mountains (Eitner 1901) belongs to a different Lecidea species. Recently, this lichen has been recorded in ca. 10 localities from lowlands to mountains. As it is a partly pioneer species, its occurrence in the Czech Republic may be underestimated. In the field, it can be easily confused with common lichens, such as Porpidia crustulata or Micarea erratica (Arup 2004).

Literature: Eitner E. (1901): II. Nachtrag zur schlesischen Flechtenflora. – Jahresbericht der Schlesischen Gesellschaft für Vaterländische Kultur, Abt. Zool.-Bot., Breslau, 78: 5–27. Hertel H. (1995): Schlüssel für die Arten der Flechtenfamilie Lecideaceae in Europa. – Bibliotheca Lichenologica 58: 137–180. Arup U. (2004): Three overlooked Lecidea species in Sweden. – Symbolae Botanicae Upsalienses 34: 39–48. Hertel H. (2009): A new key to cryptothalline species of the genus Lecidea (Lecanorales). ‒ Bibliotheca Lichenologica 99: 185‒204. Westberg M., Moberg R., Myrdal M., Nordin A. & Ekman S. (2021): Santesson’s Chec­klist of Fennoscandian Lichen-Forming and Lichenicolous Fungi. ‒ Uppsala University: Museum of Evolution.

Ascomycota → Lecanoromycetes → Lecanorales → Lecideaceae → Lecidea