ITALIC 8.0

Porpidia grisea Gowan

Bryologist, 92, 1: 48, 1989.

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Distribution:

Description: Thallus crustose, episubstratic, medium grey, usually consisting of areoles dispersed on a black hypothallus, 0.1-0.8 mm thick, forming up to 15 cm wide patches. Medulla white, I+ blue. Apothecia lecideine, up to (0.4-)0.8-1.5(-2.2) mm across, at first semi-immersed then sessile and slightly constricted at base with a flat to rarely strongly convex, black but usually grey-pruinose disc and distinct, raised, sometimes finally excluded proper margin. Proper exciple black or dark brown, up to 175 µm wide, without crystals, with parallel-radiating, c. 4 µm thick hyphae; epithecium greenish brown, often with crystals, K-, N+ orange-red; hymenium colourless, 70-100(-130) µm high, I+ blue; paraphyses coherent, weakly branched and anastomosing; hypothecium blackish brown. Asci 8-spored, elongate-clavate, with a thin, outer amyloid layer and a thickened tholus penetrated by a pore, the sides of which are strongly amyloid, Porpidia-type. Ascospores 1-celled, hyaline, ellipsoid to broadly ellipsoid, (11-)15-20(-25) x (5-)6-8(-9.5) µm, surrounded by a perispore. Pycnidia black, immersed. Conidia bacilliform, 8-12 x 1 µm. Photobiont chlorococcoid. Spot tests: thallus (especially medulla) K- or K+ yellow, C-, KC-, P- or rarely P+ reddish yellow, K/UV+ mauve. Chemistry: confluentic and methylperlatolic acids.

Note: a silicicolous species resembling P. tuberculosa in the amyloid medulla and the presence of confluentic acid as a major substance, but esorediate and richly fertile, and hence more similar to P. speirea, from which it differs in the thinner, grey thallus, the sessile apothecia and the growth on non-calciferous rocks. Described from North America, it is widespread in the Holarctic region from the Arctic to temperate-alpine zones but rare, with a single record from the Eastern Alps (Austria), being also known from Northern Europe and Poland (Jabłońska 2010). To be looked for in the Italian Alps.

Growth form: Crustose

Substrata: rocks

Photobiont: green algae other than Trentepohlia

Reproductive strategy: mainly sexual

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Poleotolerance:

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Altitudinal distribution:

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Predictive model

Erkka Laine, Luomus CC BY-NC - Sample H9238121