ITALIC 8.0

Rehmia postuma (Nyl.) E.J. Möller, Timdal, Haugan & Bendiksby

Fungal Syst. Evol, 16: 224, 2025. Basionym: Lecidea postuma Nyl. - Flora (Regensburg), 51: 345, 1868.

Synonyms: Rhizocarpon postumum (Nyl.) Arnold

Distribution: N - Frl (Nascimbene & al. 2021).

Description: Thallus crustose, very thin, cracked to areolate, grey-brown to pale brown, epruinose, rarely delimited by a black prothallus, forming 1-2 cm wide patches often delimited by a dark prothallus. Areoles up to 0.2 mm wide, flat to slightly convex, smooth. Medulla white, I-. Apothecia lecideine, innate to slightly sessile, (0.2-)0.3-0.5(-0.7) mm across, with a black-brown to black, somehow shiny, flat to finally convex, smooth disc and an up to 0.1 mm thick, usually not raised but persistent, black proper margin. Proper exciple of radiating hyphae, the outer cells olive-brown to blackish green, K-; epithecium brown, K-, with crystals soluble in K; hymenium colourless, (60-)83-145(-175) µm high, I+ blue; paraphysoids slender, scarcely swelling at apex, without a strongly delimited pigmented cap; hypothecium brown. Asci 8-spored, clavate, fissitunicate, with a well-developed tholus that is K/I- in lower part and K/I+ blue near the apex, lacking an ocular chamber, Rhizocarpon-type. Ascospores weakly submuriform (with (4-)5-7 cells in optical view), hyaline, ellipsoid, (15-)17-25(-28) x (8-)9-12(-13) µm, halonate. Photobiont chlorococcoid. Spot tests: medulla K+ yellow, C-, KC-, P+ yellow (reactions best visible on thallus sections under the microscope). Chemistry: medulla with often low amounts of stictic acid.

Note: a species recalling Rhizocarpon distinctum in the small-sized apothecia, but medulla not amyloid and with stictic acid; on siliceous rocks, often close to streams and waterfalls; widespread in Europe, but rather rare or not always distinguished, with scattered records from the Alps.

Growth form: Crustose

Substrata: rocks

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: extremely 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

DOLICHENS

Photo by Einar Timdal - Source: https://nhm2.uio.no/lav/web/index.html

Norway, Hordaland - O-L-38259

Einar Timdal, Natural History Museum, University of Oslo, Norway - CC BY-NC