Arthonia mediella Nyl.

Not. Sällsk. Fauna Fl. Fenn. Förh., ny ser. 1: 238, 1859.
Synonyms: Arthonia sordaria Körb.
Distribution: N - TAA (Nascimbene 2003, 2014, Nascimbene & al. 2006e, 2007b, 2009, 2014, Thor & Nascimbene 2007, Nimis & al. 2015), Lomb (Nascimbene 2006), Piem (Isocrono & al. 2004), Lig (TSB 33048). C - Tosc (Benesperi & al. 2007), Umb (Ravera 1999, Ravera & al. 2006), Abr (Nascimbene & al. 2019, Gheza & al. 2021), Mol (Caporale & al. 2008). S - Cal (Nimis & Puntillo 2003, Puntillo 2011).
Description: Thallus crustose, thin, continuous to finely rimose, smooth or roughened, grey to yellowish. Apothecia arthonioid, black, round to weakly angular, 0.2-0.5 mm across, with a flat to slightly convex, dull, epruinose disc. Epithecium brown-black; hymenium colourless to pale yellow, 30-60 µm high, not inspersed with oil droplets, K-, I+ orange-yellow; paraphysoids strongly adglutinated, simple or slightly branched, thin, the apical cells capitate, 3-5 µm wide, with a dark brown cap; hypothecium reddish brown in upper part, brown-black in lower part, 30-70 µm high. Asci 8-spored, broadly clavate, semi-fissitunicate, with a large apical dome and a distinct ocular chamber, Arthonia-type. Ascospores 3(-4)-septate, slightly constricted at septa, with subequal cells, hyaline, spindle-shaped, (11-)13-16(-18) x 3-5 µm. Pycnidia dark, immersed to sessile. Conidia bacilliform, 4-6 x c. 1 µm. Photobiont trentepohlioid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: a cool-temperate to boreal-montane, probably circumpolar, early coloniser of acid bark, mostly of conifers, found both in humid Abies-Fagus forests and in open Larix stands, certainly more widespread in the subalpine belt of the Alps and extending to Calabria along the Apennines.
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)
Pioneer species

Commonnes-rarity: (info)

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


pH of the substrata:

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Solar irradiation:

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Aridity:

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Eutrophication:

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Poleotolerance:

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Altitudinal distribution:

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P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (9402)
2003/01/23



P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (9402)
2001/11/21



Domenico Puntillo; Owner: Domenico Puntillo
Italy


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