Rhizocarpon richardii (Nyl.) Zahlbr.

Cat. Lich. Univ., 4: 341, 1926. Basionym: Lecidea richardii Lamy ex Nyl. - Flora, 58: 446, 1875.
Synonyms: Rhizocarpon constrictum subsp. richardii (Nyl.) Clauzade & Cl. Roux
Distribution: C - Sar (Rizzi & al. 2011), S - Si (Brackel 2008c).
Description: Thallus crustose, episubstratic, rimose-areolate, grey to brown, often with a violet tinge, forming small patches that often coalesce into up to 5(-8) cm wide larger thalli delimited by a black prothallus. Areoles angular, contiguous, flat to slightly convex, 0.4-0.8(-1) mm wide. Medulla white, I+ blue. Apothecia lecideine, black, epruinose, to 1 mm across, orbicular to irregular in outline, with a flat to slightly convex disc and a thin, often finally excluded proper margin. Proper exciple thin, with crystals dissolving in K, brown-black in outer part, pale brown to colourless within, K-; epithecium olivaceous green to grey-black, with crystals dissolving in K, K- or K+ intensifying green; hymenium colourless, 80-100 μm high; paraphysoids strongly coherent, richly branched and anastomosing, the apica cells clavate; hypothecium dark red-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 at first 1-septate, then submuriform, slightly constricted at the primary septum, dark green or dark grey, finally dark brown, 22-32 x 14-18 μm, halonate. Photobiont chlorococcoid. Spot tests: cortex K-, C-, KC-, P-: medulla K- or K+ yellow, C+ red, KC+ red, P- or P+ orange. Chemistry: medulla with variable amounts of gyrophoric, stictic and norstictic acids.
Note: the synonymisation of Rh. constrictum with Rh. richardii by Laundon (1986), was followed by most subsequent authors, including Nimis (2016). However, Clauzade & Roux (1985), who analysed the neotype of Rh. richardii (see Roux & Coll. 2025), state that the two taxa - which they treat as subspecies - differ both in spore characters and in the ecology. Rh. richardii is an inland species with soon pigmented, finally submuriform spores, whereas Rh. constrictum is a maritime, halophilous species whose spores long remain 1-septate and hyaline (finally turning pale brown and rarely submuriform). Both Italian records are from inland habitats and – pending the examination of their spores - are provisionally attributed to Rh. richardii, a species also known from inland Corsica.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

Commonnes-rarity: (info)

Alpine belt: absent
Subalpine belt: absent
Oromediterranean belt: absent
Montane belt: absent
Submediterranean belt: very rare
Padanian area: absent
Humid submediterranean belt: very rare
Humid mediterranean belt: extremely rare
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
INDEX FUNGORUM GBIF

Leif Stridvall - Source: http://www.stridvall.se/la/galleries.php


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_richardii.htm
France, 24/10/2011 - sur rocher granitique - Corse - (20) - Ciniccia Site Archéologique De Cucuruzzu, alt. 730m


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_richardii.htm
France, 24/10/2011 - sur rocher granitique - Corse - (20) - Ciniccia Site Archéologique De Cucuruzzu, alt. 730m


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_richardii.htm
France, 24/10/2011 - sur rocher granitique - Corse - (20) - Ciniccia Site Archéologique De Cucuruzzu, alt. 730m


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_richardii.htm
France, 24/10/2011 - sur rocher granitique - Corse - (20) - Ciniccia Site Archéologique De Cucuruzzu, alt. 730m


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_richardii.htm
France, 24/10/2011 - sur rocher granitique - Corse - (20) - Ciniccia Site Archéologique De Cucuruzzu, alt. 730m


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_richardii.htm
France, 24/10/2011 - sur rocher granitique - Corse - (20) - Ciniccia Site Archéologique De Cucuruzzu, alt. 730m