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, the 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 Ca-oxalate crystals insoluble in acetone. Apothecia lecideine, black, sessile, to 1.5 mm across, often clustered, with an initially 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: cortex 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 may start the life-cycle on the thalli of Baeomyces placophyllus, later becoming autotrophic, and is the most calcium-tolerant species of the genus, often occurring over soil derived from calcareous schists and even marble. When sterile, it is indistinguishable from A. alpina. 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:


Solar irradiation:








Altitudinal distribution:


Predictive model

P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: GZU H.Mayrhofer (9796)

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