Acarospora rosulata (Th. Fr.) H. Magn.

Göteb. Vetensk.-och Vitter.-Handl., ser. 4, 28, 2: 121, 1924. Basionym: Acarospora discreta f. rosulata Th. Fr. - Lichenogr. Scand., 1, 1: 218, 1871.
Synonyms:
Distribution: N - Lomb (Anzi, Lich. Lang. 532: S-L29559).
Description: Thallus crustose, episubstratic, areolate-subplacodioid, chestnut brown to reddish brown, somehow shiny, epruinose, forming orbicular to irregular rosettes to 7 cm in diam. Areoles round to angular, slightly convex, 0.5-2 mm wide, the marginal ones often elongate and radiating, to 2 mm long and 1 mm wide. Cortex paraplectenchymatous, 25-35 μm thick, reddish brown in upper part, colourless in lower part; algal layer continuous, but the algal cells sometimes arranged in vertical columns; medulla white. Apothecia lecanorine, round to irregular in outline, 0.1-0.4(-0.5) mm across, immersed, one to many per areole, with a punctiform to slightly expanded, rough, sometimes umbonate, dark brown to black disc, and a slightly raised thalline margin, rarely with a thin parathecial ring around the disc. Proper exciple of radiating hyphae, 20-40 μm wide laterally; epithecium brown; hymenium colourless, (85-)100-140 μm high; paraphyses 1.5-2 μm thick at base, the apical cells to 4 μm wide; hypothecium colourless. Asci >200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, narrowly ellipsoid, 3-6.5 x 1.5-2 μm. Photobiont chlorococcoid. Spot tests: cortex K-, C+ pink, KC+pink (best seen in sections under the microscope), P-. Chemistry: gyrophoric acid.
Note: this species, described from Norway where it is rare, is known from western North America, Asia (Mongolia) and the French Alps. It grows on sun-exposed siliceous rocks, with optimum in dry, subcontinental areas, near or above treeline.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Subcontinental: restricted to areas with a dry-subcontinental climate (e.g. dry Alpine valleys, parts of Mediterranean Italy)

Commonnes-rarity: (info)

Alpine belt: extremely rare
Subalpine belt: extremely rare
Oromediterranean belt: absent
Montane belt: extremely rare
Submediterranean belt: absent
Padanian area: absent
Humid submediterranean belt: absent
Humid mediterranean belt: absent
Dry mediterranean belt: absent


pH of the substrata:

(info)

1

2

3

4

5

Solar irradiation:

(info)

1

2

3

4

5

Aridity:

(info)

1

2

3

4

5

Eutrophication:

(info)

1

2

3

4

5

Poleotolerance:

(info)

0

1

2

3

Altitudinal distribution:

(info)

1

2

3

4

5




Jason Hollinger –https://www.flickr.com/photos/7147684@N03/15304231354 CC BY 2.0