ITALIC 8.0

Rhizocarpon santessonii Timdal

Lichenologist, 18: 317, 1986.

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Distribution:

Description: Thallus crustose, rimose-areolate, yellowish grey, forming scattered to confluent, up to 5 mm wide patches on the thalli of Tremolecia atrata, the areoles up to 0.5 mm wide, developing inside those of the host and removing their rust colour, smooth, epruinose, irregularly rounded to angular, flat to weakly convex, without a distinct prothallus. Cortex 10-15 µm thick, densely incrusted by yellow granules not refracting polarized light, which are only slowly soluble in K, overlain by a thin epinecral layer; medulla thin or absent, I-, K/I-. Apothecia lecideine, dull black, epruinose, up to 0.7 mm across, at first flat and indistinctly marginate, later convex and immarginate. Proper exciple 20-30 µm thick, brownish black, K+ purple-red; epithecium brownish black, K+ purple-red; hymenium colourless, 60-90 μm high, I+ blue; paraphysoids richly branched and anastomosing, c. 2.5 μm thick at mid-level, the apical cell slightly swollen and usually dark brown-capped; 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, 50-60 x 12-15 μm. Ascospores 1-septate, constricted at septum, long remaining hyaline but often turning brown when overmature, 12.5-15 x 6.5-8 μm, halonate. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: cortex with an unidentified yellow pigment (not rhizocarpic acid!).

Note: an arctic to nemoral-alpine, silicicolous species growing on the thalli of Tremolecia atrata, described from Norway, with some records from the Eastern Alps (Austria). To be looked for in the Italian Alps.

Growth form: Crustose

Substrata: rocks

Photobiont: green algae other than Trentepohlia

Reproductive strategy: mainly sexual

paras Tremolecia atrata

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Predictive model

Photo by Einar Timdal - CC BY-SA 3.0 - Source: https://artsdatabanken.no/Pages/230300/

Norway