Acarospora impressula is Holarctic species known from Asia, Europe and North America on calcareous and non-calcareous rock, metal-rich rock, and roofing slates in full sun. Most collections of A. impressula in the Czech Republic are on diabase at low elevations below 300 m. It is also a high elevation species in the Alps.
Like A. atrata it forms a contiguous areolate crust up to 1 mm thick. It differs from A. atrata in having euamyloid hymenal gel, occasionally larger subconvex areoles, broadly ellipsoid ascospores (more than 2 µm wide), and thicker paraphyses (2–3 µm vs. 1.5–2.0 µm). Like A. atrata or A. insolata, the morphological species concept of A. impressula may be a complex of species.taxonomic classification:
All records: 24, confirmed 0. One click on a selected square displays particular record(s), including their source(s).