Acarospora schleicheri (aka “Soil Paint Lichen”)
Description: Thallus pale to bright sulpher yellow, sometimes pruinose, squamulose-areolate, often lobed at the margins, with large red-brown, sometimes scabrose apothecia embedded in areoles; hundreds of spores per ascus.
Chemistry: Negative to all reagents but UV+ orange (no lichen substances other than a yellow pigment, rhizocarpic acid, in the cortex).
Substrate: On stabilized soil in the open.
Range: Throughout the more arid parts of the western interior from Mexico to southern British Columbia & Saskatchewan. See distribution under A. contigua.
Lookalikes: This is the only common yellow Acarospora on soil. Because it is extremely variable in thallus development, color, amount of pruinosity, & color of the apothecia, many varieties have been given names. Some lichenologists include saxicolous populations, such as A. contigua, within A. schleicheri. Acarospora stapfiana, a yellow species made chalky white by a heavy pruina, has an areolate thallus with sunken brown apothecia; it parasitizes Caloplaca trachyphylla. Fulgensia species also produce yellow thalli on arid soil, but they can be identified, even when sterile, by their K+ deep purple reaction.
Bibliography: Lichens of North America, by Brodo, Sharnoff, & Sharnoff
Database Entry: Distance Everheart 12-26-13