Calogaya arnoldii (Wedd.) Arup, Frödén & Søchting subsp. arnoldii

in Arup & al., Nord. J. Bot., 31: 38, 2013. Basionym: Lecanora arnoldii Wedd. - Bull. Soc. Bot. France, 23: 96, 1876.
Synonyms: Amphiloma murorum var. gyalolechioides auct. ital. p.p.; Caloplaca arnoldii (Wedd.) Zahlbr. ex Ginzb. non auct.ital.; Caloplaca biatorina subsp. gyalolechioides auct. p.p.; Caloplaca biatorinoides; Caloplaca saxicola subsp. arnoldii (Wedd.) Clauzade & Cl. Roux non auct.ital.; Caloplaca saxicola subsp. biatorinoides Clauzade & Cl. Roux; Physcia pusilla var. lobulata f. minor Arnold; Placodium murorum f. arnoldii (Wedd.) A.L. Sm.
Distribution: N - VG, Ven, TAA (Nascimbene & al. 2021). C - Tosc (TSB 34239), Umb (Ravera & al. 2006). Mol (Genovesi & Ravera 2014), Sar.
Description: Thallus crustose-placodioid, episubstratic, forming orbicular rosettes to 1 cm in diam., reddish-orange to orange (yellow in shade-forms), usually abundantly pruinose. Central part of thallus with 0.3-1.3 mm wide, strongly convex, irregular to elongate areoles formed by lobe fragmentation. Marginal lobes convex, irregular or finger-like, slightly broadening at tips, with short and often forked terminal branches, 0.1-1(-1.5) mm long, 0.1-0.6(-0.9) mm wide. Upper cortex with a 6-18.5(-22.5) μm thick brownish-orange upper layer, and a hyaline (6-)10-45(-50) μm thick intemal layer of irregularly arranged hyphae; medulla lax. Apothecia common, zeorine, more or less crowded, 0.13- 0.7(-0.9) mm across, round or slightly deformed by mutual compression, located either on the areoles or on the lobe bases, sessile to constricted at base. Disk flat to strongly convex, concave in young apothecia, reddish-orange to brownish, somewhat pruinose, smooth; margin paler than disk, without differentiation between proper and thalline margin, slightly pruinose, smooth, 25-100 μm thick. Epithecium 6-12 μm thick, brownish-orange K+ red; hymenium, subhymenium and hypothecium colourless; paraphyses distinctly septate, forked or subapically branched, often anastomosing, (1.2-)1.5-3.5(-4) μm wide at base, the apical cells (2.5-)3.5-7.5(-8)μm wide. Asci 8-spored, clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, narrowly ellipsoid, (7.5-)9.5-13(-15) x (3.5-)4.5-5.5(-6.5) μm, the septum (2-)3-4.5(-5) μm thick. Photobiont chlorococcoid. Spot tests: thallus and apothecia K+ red, C-, KC-, P-. Chemistry: thallus and apothecia with parietin (major), fallacinal, emodin, teloschistin and parietinic acid (minor), corresponding with chemosyndrome A of Søchting (1997).
Note: a well-distinct taxon of the extremely critical C. saxicola complex, found on steeply inclined surfaces of calciferous rocks (limestone, dolomite, calcareous schists) in open habitats; certainly more widespread in Italy. For further details see Gaya & al. (2001).
Growth form: Crustose placodiomorph
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

Commonnes-rarity: (info)

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


pH of the substrata:

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Solar irradiation:

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Eutrophication:

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Poleotolerance:

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Altitudinal distribution:

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Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene



Elena Pittao - CC BY-SA 4.0
Italy, Abruzzo, AQ, Rocca Calascio.
Herbarium: TSB (26383)



Pier Luigi Nimis - CC BY-SA 4.0
TSB 37997



Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene



Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene



Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene



Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene



P.L. Nimis CC BY-SA 4.0
TSB 9055



Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene



Pier Luigi Nimis - CC BY-SA 4.0
Italy, Trentino-Alto Adige
Herb. J. Nascimbene