Arthrorhaphis vacillans Th. Fr.

Th. Fr. & Almq. ex Th. Fr., Bot. Not.: 107, 1867.
Synonyms: Arthrorhaphis anziana (Lynge) Poelt; Bacidia anziana Lynge; Bacidia vacillans (Th. Fr.) Rostr.
Distribution: N - TAA.
Description: Thallus crustose, areolate to verrucose, forming a compact crust. Areoles at first pale greenish yellow, then bright yellow-green, thick, 1-2 mm wide, flat to usually strongly convex, contiguous, with an epinecral layer. Medulla well-developed, white to yellowish, filled with oxalate crystals (insoluble in acetone). Apothecia lecideine, sessile, to 1.5 mm across, with a black, at first concave then soon flat, smooth disc and a thin, smooth, black proper margin. Exciple brown-black in outermost part, blue-green within; epithecium and hypothecium dark grey green, K-, N+ emerald green; hymenium colourless, inspersed with oil droplets, I-; paraphyses lax, slender, branched and anastomosing, not apically thickened, c. 1.5 µm thick. Asci 4-6(-8)-spored, bitunicate, clavate, I-, scarcely thickened at apex, with a small ocular chamber. Ascospores 3(-4)-septate, hyaline, fusiform, thin-walled, (14-)16-22(-25) x 3-3.5(-4) µm. Photobiont chlorococcoid. Spot tests: thallus and medulla K-, C-, KC-, P-, UV+ orange. Chemistry: rhizocarpic acid, epanorin, and sometimes traces of atranorin.
Note: an arctic-alpine, circumpolar species found in humid soil near and above treeline. It starts the life-cycle as a parasite of Baeomyces placophyllus, later becoming autotrophic, and is the most calcium-tolerant among the Arthrorhaphis-species, often occurring over calcareous schists and even marmor (Obermayer in litt.). Probably more widespread in the Alps.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
paras Baeomyces placophyllus

Commonnes-rarity: (info)

Alpine belt: very rare
Subalpine belt: rare
Oromediterranean belt: absent
Montane belt: absent
Submediterranean belt: absent
Padanian area: absent
Humid submediterranean belt: absent
Humid mediterranean belt: absent
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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P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: GZU H.Mayrhofer (9796)
2003/04/28



P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: GZU H.Mayrhofer (9796)
2003/04/28
on the thallus of the host, Baeomyces rufus