Acarospora episulphurata Cl. Roux & S. Poumarat

in Roux & al., Bull. Soc. linn. Provence, 70, 1: 161, 2019
Description: Thallus crustose, episubstratic, areolate-subsquamulose, chestnut brown, epruinose, rather glossy, developing on the thalli of Acarospora sulphurata. Areoles angular to rounded, 0.3-1.3 mm wide, mostly flat, scattered or contiguous and gather in small, rarely large groups, the margins at first dark, then whitish. Cortex paraplectenchymatous, brown in upper part, 30-50 µm thick, with an epinecral layer, the unpigmented lower part filled with crystals; algal layer continuous, __ – 40-75 μm thick; medulla white, filled with large crystals. Apothecia lecanorine-aspicilioid, immersed in the areoles, round to elliptical in outline, 0.1-0.4 mm across, with an initially punctiform then expanded, dark brown, epruinose, rugose, concave to flat disc, without a distinct margin. Proper exciple continuous with the hypothecium; epithecium brown; hymenium colourless, 80-90 µm high, I+ deep blue; paraphyses sparingly branched and anastomosing, 1.5-2 µm thick at base, the apical cells 2.5-3.5 µm wide, with a distinct brown cap; hypothecium colourless, prosoplectenchymatous. Asci c. 100-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, broadly ellipsoid to subglobose, 4-6.5 x (3.5-)4-6(-6-5) µm. Photobiont chlorococcoid. Spot tests: cortex K-, C+ red, KC+ red, P-. Chemistry: gyrophoric acid.
Note: a recently-described species growing on the thalli of Acarospora sulphurata on steeply inclined, sunny surfaces of siliceous rocks; known from Spain and France, to be looked for in Italy, especially in the xerothermic Alpine valleys.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
paras Acarospora sulphurata

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Predictive model

Serge Poumarat - Source:
France, Alpes de Haut-Provence