Arthonia granosa B. de Lesd.

Bull. Soc. Bot. France, 53: 518, 1906.
Distribution: C - Laz (Ravera 2002b), Sar (Sundin 1999, Zedda 2002, Rizzi & al. 2011, Di Nuzzo & al. 2022). S - Camp (Ravera & al. 2018), Pugl (Nimis & Tretiach 1999), Si (CLU 16121).
Description: Thallus crustose, probably not lichenized, mostly endosubstratic and inapparent, or forming grey-white patches. Apothecia arthonioid, black but often grey-pruinose, round to slightly ellipsoid, 0.2-0.5 µm across, immersed to erumpent, up to 100 µm tall. Proper exciple poorly developed; epithecium reddish brown, 10-20 µm high; hymenium colourless, 30-60 µm high, with granules, I+ red, K/I+ blue; paraphysoids 1-1.5 µm thick; hypothecium colourless, 5-10 µm high. Asci 8-spored, globose to broadly clavate, semi-fissitunicate, with a large apical dome, a distinct ocular chamber, and an inconspicuous ring-structure in tholus, Arthonia-type. Ascospores 1-septate, not constricted at septum, hyaline, broadly ovoid, 17-25(-30) x 8-12 µm, without an epispore. Pycnidia up to 0.1 mm wide. Conidia bacilliform, 3-5 x c. 1 µm. Photobiont probably absent. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: thallus without lichen substances.
Note: a Mediterranean-Atlantic epiphytic species restricted to coastal situations with humid maritime winds, generally on Juniperus, but also on Olea and Quercus ilex. Perhaps non-lichenised. It is included in the Italian red list of epiphytic lichens as “Vulnerable” (Nascimbene & al. 2013c).
Growth form: Crustose
Substrata: bark
Photobiont: Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)
Taxon bound to maritime-coastal situations

Commonnes-rarity: (info)

Alpine belt: absent
Subalpine belt: absent
Oromediterranean belt: absent
Montane belt: absent
Submediterranean belt: absent
Padanian area: absent
Humid submediterranean belt: absent
Humid mediterranean belt: very rare
Dry mediterranean belt: extremely rare

pH of the substrata:


Solar irradiation:








Altitudinal distribution:


Predictive model
Herbarium samples

P.L. Nimis CC BY-SA 4.0
TSB 13225

Redinger, K. (1938) Arthoniaceae, Graphidaceae . In Kryptogamen-Flora von Deutschland, Österreich und der Schweiz. Band 9, 2 Abt., Part 1 (G. L. Rabenhorst, ed.): 181–404. Leipzig: Borntraeger