Biatoropsis usnearum s.l. Räsänen
Basidiomycete (BASIDIOMYCOTA) parasite of Usnea.
Species looks as an almost spherical gall with a narrowed base 0.5-2 mm in diameter, smooth, pinkish, pale reddish-brown. Basidiospores very broadly elliptical to subglobose with a very distinct apiculus, 4.5-8 x 4-7.5 µm arising from basidia 1-3 times septate. Parasitic of many Usnea species. Species not especially maritime but quite common and sometimes very abundant on Usnea along the seashore and in oceanic woods and forests.
N.B. It is preferable to speak of the "complex" of Biatoropsis usnearum because it seems that in our prospecting region exist two species that are indistinguishable other than by biomolecular analysis: Biatoropsis usnearum ss. str. and Biatoropsis hafelneri Millanes, Diederich, Westb. & Wedin., see for more details: Three news species in the Biatoropsis usnearum complex. Ana M. Millanes, Paul Diederich, Martin Westberg & Mats Weden. Herzogia 29 (2) Teil 1, 2016: 337-354.
N.B. It was recently isolated from this complex: Cyphobasidium usneicola which is distinguished, in addition to its microscopic characters, by its pinkish muriform galls, particularly well developed on Usnea articulata.