Thelocarpon impressellum Nyl.

Flora, 50: 179, 1867.
Synonyms:
Distribution: N - TAA (Arnold 1887, Brackel 2016, Nascimbene & al. 2022).
Description: Thallus doubtfully lichenized, reduced to bright yellow-pruinose fertile warts. Ascocarps globose, 0.15-0.4 mm across, up to 0.2 mm high, perithecioid when young, later with a minute, expanded disc, immersed in the warts. Exciple 40-70 μm thick at apex, 30-50 μm thick in lower part, colourless in section; hymenial gel I+ red, K/I+ blue; paraphyses mostly simple, rarely slightly branched and anastomosing, slender, longer than the asci. Asci many-spored, spindle-shaped, tapering to apex, the wall I+ pale blue in upper part, the apex thickened into a tholus with a I+ blue ring-structure within. Ascospores 1-celled, hyaline, oblong 6-8.5(-11) x 4-5 μm. Photobiont absent. Spot tests: K-, C-, KC-, P-. Chemistry: yellow pruina on the ascocarps with pulvinic acid derivatives.
Note: a doubtfully lichenised species found on humus-rich soil, mosses, rotten wood and other lichens in upland areas. The only Italian record, referring to a sample growing on Squamarina cartilaginea, is dubious.
Growth form: Crustose
Substrata: lignum, soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

Commonnes-rarity: (info)

Alpine belt: very rare
Subalpine belt: very rare
Oromediterranean belt: absent
Montane belt: absent
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

Felix Schumm - CC BY-SA 4.0
[19100], Germany, Nordrhein-Westfalen, Niederrheinisches Tiefland, Duisburg, auf Algenbelägen über steinigem Sandboden der Industriebrache Landschaftspark Duisburg-Nord, ca. 30 m. TK: 4506/2. Leg. et det. D.G. Zimmermann 6.12.2012.


Felix Schumm - CC BY-SA 4.0
[19100], Germany, Nordrhein-Westfalen, Niederrheinisches Tiefland, Duisburg, auf Algenbelägen über steinigem Sandboden der Industriebrache Landschaftspark Duisburg-Nord, ca. 30 m. TK: 4506/2. Leg. et det. D.G. Zimmermann 6.12.2012.


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_T/Textes_T2/Thelocarpon_impressellum.htm
France, 14/9/2015 - Flaines, les grandes platières - Haute-Savoie


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_T/Textes_T2/Thelocarpon_impressellum.htm
France, 14/9/2015 - Flaines, les grandes platières - Haute-Savoie


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_T/Textes_T2/Thelocarpon_impressellum.htm
France, 14/9/2015 - Flaines, les grandes platières - Haute-Savoie