Arthonia didyma Körb.

Denkschr. schles. Ges. vaterl. Kultur: 235, 1853.
Synonyms: Arthonia aspersella Leight.; Arthonia atrofuscella Nyl.; Arthonia pineti Körb.; Arthonia sapineti Nyl.; Caldesia didyma (Körb.) Trevis.
Distribution: N - Ven, TAA (Nascimbene & al. 2007b, 2014, Nascimbene 2014), Lomb, Piem (Piervittori 2003, Isocrono & al. 2004, Giordani & Malaspina 2016). C - Tosc (Stofer 2006, Brunialti & Frati 2010, Brunialti & al. 2012b), Umb (Ravera 1998, Ravera & al. 2006), Laz (Ravera 2001, 2006c, Nimis & Tretiach 2004, Stofer 2006), Abr (Nimis & Tretiach 1999, Corona & al. 2016), Mol (Caporale & al. 2008, Ravera & Genovesi 2010, Ravera & al. 2010), Sar (Rizzi & al. 2011, Cossu 2013). S - Pugl (Nimis & Tretiach 1999), Bas (Potenza 2006, Potenza & al. 2010, Potenza & Fascetti 2012), Cal (Puntillo 1996).
Description: Thallus crustose, mostly endosubstratic and inconspicuous, pale brown or olive-grey, sometimes with a pink hue when fresh. Apothecia arthonioid, immarginate, more or less immersed, rounded, shortly ellipsoid or weakly and irregularly lobed, 0.1-0.5 mm wide, 45-70 μm tall, with a dark brown to brown-black, epruinose, mostly flat disc. Epithecium yellowish brown to reddish-brown, c. 5 μm high, K+ purple-violet, the pigments dissolving; hymenium colourless to spottily pale orange-brown, the pigmented parts K+ purple-violet, 33-50 μm high; paraphysoids 0.5-1.5 μm thick, brown-walled, the apical cells to 2.5 μm wide; hypothecium red-brown, 5-30 μm high, the pigment K+ grey or olive. Asci 8-spored, subglobose, semi-fissitunicate, with a large apical dome and a distinct ocular chamber, Arthonia-type. Ascospores 1-septate and slightly constricted at septum, with subequal to unequal cells, at first hyaline and smooth, later brownish and warted, ovoid, (12-)14-18 x 4-8 μm, thick-walled, but without a gelatinous sheath. Pycnidia rare, immersed, the wall red-brown, K+ olive-grey. Conidia bacilliform, 3.5-4 x c. 0.7 μm. Photobiont trentepohlioid. Spot tests: K-, C-, KC-, P-. Chemistry: thallus without lichen substances; anthraquinones in pigmented parts of the apothecia.
Note: a cool-temperate species found on smooth, acid bark in humid areas, most frequent in the beech belt of Tyrrhenian Italy.
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)

Commonnes-rarity: (info)

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


pH of the substrata:

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Poleotolerance:

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Altitudinal distribution:

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P.L. Nimis CC BY-SA 4.0
TSB 22890



Felix Schumm – CC BY-SA 4.0
[14965], Germany, Baden-Württemberg, Kreis Tübingen, zwischen Dettenhausen und Bebenhausen, bei der Bärlochhütte im schattigen Buchenwald, 450 m



Felix Schumm – CC BY-SA 4.0
[19622], Germany, Baden-Württemberg, Kreis Göppingen, am Parkplatz nahe der Zachersmühle im Heiligenwald, auf Laubbaum, 48.75277° N, 9.61983° E, 364 m. Leg. et det. F. Schumm, 07.02.2017



Felix Schumm – CC BY-SA 4.0
[19622], Germany, Baden-Württemberg, Kreis Göppingen, am Parkplatz nahe der Zachersmühle im Heiligenwald, auf Laubbaum, 48.75277° N, 9.61983° E, 364 m. Leg. et det. F. Schumm, 07.02.2017



Felix Schumm – CC BY-SA 4.0
[19622], Germany, Baden-Württemberg, Kreis Göppingen, am Parkplatz nahe der Zachersmühle im Heiligenwald, auf Laubbaum, 48.75277° N, 9.61983° E, 364 m. Leg. et det. F. Schumm, 07.02.2017


Photo uploaded by P. Cannon, CC BY-SA NC Source: http://fungi.myspecies.info/file/12736


Photo uploaded by P. Cannon, CC BY-SA NC Source: http://fungi.myspecies.info/file/12736


Photo uploaded by P. Cannon, CC BY-SA NC Source: http://fungi.myspecies.info/file/12426


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


Zahlbruckner A. 1926. Lichenes (Flechten). In: Engler A. (ed.): Die natürlichen Pflanzenfamilien. 2nd ed., vol 8, W. Engelmann, Leipzig, 270 pp.



Felix Schumm – CC BY-SA 4.0
[14981], Germany, Baden-Württemberg, Kreis Göppingen, Marbachtal an Fagus, 350 m.