ITALIC 8.0

Rhizocarpon vulgare Timdal, E.J. Möller & Bendiksby

Graphis Scripta, 36, 4: 101, 2024.

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Distribution:

Description: Thallus crustose, episubstratic, grey to grey-brown, areolate, forming up to 10 cm wide patches delimited by a black prothallus, the areoles more or less contiguous, orbicular or angular to slightly crenulate, flat to usually convex. Medulla I-, K/I-. Apothecia black, epruinose, up to 1 mm across, orbicular, with a more or less flat disc and a thin proper margin. Proper exciple blackish brown, K+ purple-red or K-; epithecium dark brown, thin, sharply delimited, without crystals and granules, K+ rather faintly purple-red; hymenium colourless; paraphysoids branched and anastomosing; hypothecium brown, K-. 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 1-septate, soon dark brown, ellipsoid, 26-35 x 12-17 µm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC- P-. Chemistry: medulla with diffractaic acid.

Note: a recently-described species resembling Rh. badioatrum but differing in often forming more rounded, convex, and greyish areolae; in having a more narrow and more sharply delimited epithecium with a less intense K+ red reaction, and especially in containing diffractaic acid. The species seems to be widespread in Scandinavia, with several records in Central and Southern Europe, e.g. in Slovakia (Timdal & al. 2024) and France, including Corsica (Roux & Coll. 2025). It should be looked for also in Italy (specimens of Rh. badioatrum should be chemically analysed).

Growth form: Crustose

Substrata: rocks

Photobiont: green algae other than Trentepohlia

Reproductive strategy: mainly sexual

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Eutrophication:

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Poleotolerance:

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Altitudinal distribution:

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Predictive model

Source: Timdal, E., Möller, E. J. & Bendiksby, M. 2024. Rhizocarpon vulgare, a new species in the R. badioatrum species complex. Graphis Scripta 36 (4): 89–105. Oslo. ISSN 2002-4495. - CC BY-4.0

holotype. Norway, specimen 29 in Table 1 (O L-163823). Bar = 2 mm