Lecidea grisella sympatric with Lecidea fuscoatra, differing in its rimose instead of areolate thallus

Extract

Lecidea fuscoatra (L.) Ach. is one of the earliest lichen species described, and is very common and widespread in Europe. Lecidea grisella Flörke, described from Germany, was kept separate at species level in many floras until the 1950s. In recent lichen floras, however, and in the most recent key to the genus (Hertel 1995), L. grisella is no longer accepted at species level, although it is keyed out and recognized by Hertel as L. fuscoatra var. grisella (Floerke) Nyl. The main difference is usually reported to be the thallus colour; brown and shiny in L. fuscoatra, grey and opaque in L. grisella. Some authors, for example Hertel (1995) and Wirth (1995), report that the two taxa have different habitat preferences: L. fuscoatra occurring mainly on acid substrata, while L. grisella is reported to prefer more neutral, often dust-impregnated rock and to be common on roof tiles.