Verrucaria tectorum (A. Massal.) Körb.

Parerga Lichenol., 4: 368, 1863 (1865). Basionym: Lithocia tectorum A. Massal. - Symmicta Lich.: 91, 1855.
Synonyms: Verrucaria nigrescens f. tectorum (A. Massal.) Coppins & Aptroot; Verrucaria viridula f. tectorum (A. Massal.) J.R. Laundon
Distribution: N - VG (Castello 2002, Martellos & Castello 2004), Frl (Nimis & Salvadori 1998, Nascimbene & al. 2009b), Ven (Lazzarin 2000b), Lomb (Favero-Longo & al. 2023), Piem, VA (TO 3015), Emil (Nimis & al. 1996, Fariselli & al. 2020), Lig (Valcuvia & al. 2000). C - Marc (Nimis & Tretiach 1999), Umb (Panfili 2000, Ravera & al. 2006), Abr (Nimis & Tretiach 1999). S - Camp (Garofalo & al. 1999, 2010, Ricciardi & al. 2000, Nimis & Tretiach 2004), Pugl (Garofalo & al. 1999, Nimis & Tretiach 1999), Bas (Nimis & Tretiach 1999).
Description: Thallus crustose, episubstratic, cracked-areolate, well-delimited, chestnut brown to black-brown, epruinose, 0.1-0.3 mm thick, the areoles 0.2-1 mm wide, subdivided into often superimposed smaller units by shallow cracks, flat to slightly convex, the margins densely covered by dark, corticate blastidia (best visible in the wet state). Cortex paraplectenchymatous, 5-10 µm thick, brown; algal layer 50-150 µm thick; medulla more or less brown-pigmented, but not forming a carbonaceous black basal layer. Perithecia very small, entirely immersed or slightly projecting with the up to 0.2 mm wide apical part. Involucrellum appressed to exciple, extending to base-level and merging with the dark basal layer; exciple subglobose, 0.2(-0.3) mm across, the wall dark brown; hamathecium of c. 25 µm long periphyses, interascal filaments absent; hymenial gel hemiamyloid, I+ red (I+ blue at very low concentrations of I), K/I+ blue. Asci 8-spored, clavate, I-, fissitunicate, the wall thickened above, with an ocular chamber, dehiscent by extrusion of an endotunica to form a delicate rostrum, Verrucaria-type. Ascospores 1-celled, hyaline, ellipsoid, 17–23 × 10–11 μm. Pycnidia fully immersed, c. 70 μm across. Conidia short-cylindrical, 1–2 μm wide. Photobiont chlorococcoid. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: mainly on man-made substrata, including mortar walls. Frequently confused with V. macrostoma f. furfuracea and with blastidate morphs of V. nigrescens (see Breuss & Berger 2010 and Roux & coll. 2025). Most Italian records need confirmation.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by isidia, or isidia-like structures (e.g. schizidia)
Pioneer species

Commonnes-rarity: (info)

Alpine belt: rather common
Subalpine belt: common
Oromediterranean belt: common
Montane belt: extremely common
Submediterranean belt: extremely common
Padanian area: common
Humid submediterranean belt: extremely common
Humid mediterranean belt: extremely common
Dry mediterranean belt: very common

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
DOLICHENS

Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, L'Aber


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, Landevennec


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, Rostellec


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, Rostellec


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, Rostellec


Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, L'Aber


Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, L'Aber


Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, L'Aber


Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, L'Aber


Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=973&lang=en
France, L'Aber


Source: https://www.europeana.eu/en/item/854/NHMUKXBOTXBM001107163
Verrucaria tectorum (A.Massal.) Körb. - The Trustees of the Natural History Museum, London, United Kingdom - CC BY. - isotype


Zschacke, H. (1934) Epigloeaceae, Verrucariaceae und Dermatocarpaceae. In: Dr. L. Rabenhorst‘s Kryptogamen-Flora, Band 9, Abt. 1, Teil 1. Akademische Verlagsgesellschaft, Leipzig, 695 pp. - Public Domain