Rhizocarpon constrictum Malme

Svensk Bot. Tidskr., 13, 1: 30, 1919.
Synonyms: Rhizocarpon atlanticum I. M. Lamb; Rhizocarpon richardii subsp. constrictum (Malme) Cl. Roux
Distribution:
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 1-septate, finally sometimes submuriform, strongly constricted at the primary septum, long remaining hyaline, finally pale brown, 18-29 x 11-20 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). To be looked for in Italy.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)
Taxon bound to maritime-coastal situations

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Predictive model

Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Lagatjar
As Rh. richardii


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_constrictum.htm
France, 12/10/2018 -Tour de capitello, rochers crique bord de plage, alt. 3 m Grosseto-Prugn - Corse - (20) -


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_constrictum.htm
France, 12/10/2018 -Tour de capitello, rochers crique bord de plage, alt. 3 m Grosseto-Prugn - Corse - (20) -


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_constrictum.htm
France, 12/10/2018 -Tour de capitello, rochers crique bord de plage, alt. 3 m Grosseto-Prugn - Corse - (20) -


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_constrictum.htm
France, 12/10/2018 -Tour de capitello, rochers crique bord de plage, alt. 3 m Grosseto-Prugn - Corse - (20) -


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Ouessant
As Rh. richardii


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Ouessant
As Rh. richardii


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Pointe de Pen-Hir
As Rh. richardii


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Pointe de Pen-Hir
As Rh. richardii


Courtesy Danièle et Olivier Gonnet - Source: https://www.afl-lichenologie.fr/Photos_AFL/Photos_AFL_R/Textes_R2/Rhizocarpon_richardii_constrictum.htm
France, Excursion AFL 2008 - Finistère


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Ile Vierge
As Rh. richardii


Bernard Bouffinier - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Cap de la Chèvre
As Rh. richardii


Alain Gerault - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Dinan Nord
As Rh. richardii


Michel David - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Pointe de Pen-Hir
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii


Jacques Haine - Source: http://www.lichensmaritimes.org/index.php?task=fiche&lichen=51&lang=en
France, Crozon
As Rh. richardii