Acarospora impressula Th. Fr.

Lichenogr. Scand., 1, 1: 214, 1871.
Synonyms: Acarospora atrata Hue; Acarospora hospitans f. insolita Asta & Cl. Roux nom. inval.
Distribution: N - Frl (Tretiach & Hafellner 2000), TAA (Nascimbene 2003), Piem (Giordani & al. 2014, Favero-Longo & al. 2015), VA (Piervittori & al. 2004, Isocrono & al. 2008, Favero-Longo & Piervittori 2009, Matteucci & al. 2015c).
Description: Thallus crustose, episubstratic, rimose-areolate, forming small, up to 2(-3) cm wide patches, often on other epilithic lichens. Areoles 0.5-1.5(-2.5) mm wide, contiguous, sharply angular or elongate, dark brown to black-brown, slightly concave to slightly convex, the marginal ones not radiating; lower surface dark. Medulla whitish grey, containing many crystals; algal layer continuous. Apothecia lecanorine, deeply immersed in the areoles, angular to oval-elongate, 0.2-0.3(-0.5) mm wide, 1-3(-5) per areole, with an initially punctiform, later sometimes elongate, concave to flat disc which is usually darker than thallus, a thin, shiny, swollen thalline margin, and often a distinctict parathecial ring. Proper exciple expanding around the disc, up to 40 μm thick; epithecium brown; hymenium colourless, 60-90(-130) μm high, euamyloid, K/I+ blue; paraphyses stout, 2-3 μm thick at mid-level, the apical cells 2-4 μm wide; hypothecium colourless. Asci c. 100-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, broadly ellipsoid, 3-5 x (1.5-)2-2.5 μm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: an arctic-alpine to boreal-montane, probably circumpolar species found on metal-rich rocks and roofing slates, more rarely on weakly calciferous siliceous rocks, usually in upland areas, with optimum above treeline. Probably overlooked and more widespread in the Alps. The record from Sicilia by Grillo & Caniglia (2004), being dubious, is not accepted here. The species does not belong to Acarospora s.str. (Westberg & al. 2015).
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
paras crustose lichens especially Aspicilia polychroma
Species of metal-rich rocks

Commonnes-rarity: (info)

Alpine belt: rare
Subalpine belt: very 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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Predictive model
Herbarium samples


Pier Luigi Nimis CC BY-SA 4.0
TSB 41610



P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (32814)
2001/12/12



P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (32814)
2001/12/12
apothecia


Author: Harrie Sipman - Source: http://www.bgbm.fu-berlin.de/sipman/Zschackia/AegeanLichens/Acarospora.htm



Pier Luigi Nimis CC BY-SA 4.0
TSB 41610



Pier Luigi Nimis CC BY-SA 4.0
TSB 41610


Magnusson A. H. (1935) Acarosporaceae, Thelocarpaceae. - In: Rabenhorst G. L.: Kryptogamen-Flora von Deutschland, Österreich, und der Schweiz-. 2nd- IX. Die Flechten. Abt. 5- 1. Gebr. Borntraeger. Leipzig, pp. 1-318. – Public Domain