Acarospora hellbomii is a rare species described from three collections in Sweden on granite. It is a poorly known in need of a revision. It has distinctive appearance forming scattered clusters of shiny brown squamules 1–10 mm with small brown apothecia 0.2–0.4 mm wide. The cortex is 20–40 µm thick and is C+ red (gyrophoric acid). Its diagnostic characters are the shiny brown color, the clustered thallus with small apothecia, and especially euamyloid hymenial gel (IKI+ dark blue). The only C+ species in central Europe with euamyloid hymenial gel are A. gallica and A. hellbomii.
It is apparently extremely rare but possibly has been misidentified as A. squamulosa (misapplied name A. peliocypha). Acarospora hellbomii is known in the Czech Republic only from a single sequenced collection on gneiss near Dívčí kámen in South Bohemia. Acarospora hellbomii is not a synonym of A. marcii H. Magn., a French species, that resembles A. veronensis or A. fuscata according to Magnusson (1929). Magnusson annotated one specimen as A. marcii from Germany (Wirth et al. 2013), which was not hellbomii.
Literature: Magnusson A.H. (1929): A monograph of the genus Acarospora. – Kungliga Svenska Vetenskaps-Akademiens Handlingar 7: 1–400. Wirth V., Hauck M. & Schultz M. (2013): Die Flechten Deutschlands. – Ulmer, Stuttgart.taxonomic classification:
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