Arthothelium scandinavicum
Arthothelium scandinavicum collected from Picea abies at Hellerud Ø in Sigdal (O-L-222317).
Arthothelium scandinavicum is the only Norwegian Arthothelium species that preferably grows on spruce. It is characterized by maculate, brownish black apothecia with often patches of orange pruina, and a thin whitish thallus with a trentepohlioid photobiont. The brown and warted spores are divided by 5–7 transverse and 1–4 longitudinal septa. The apical cell is not enlarged.
- Innhold
- Description
- Ecology
- Distribution in Norway and the Nordic countries
- Global distribution
- Similar species
Description
Thallus
The thin and indistinct thallus discolors the host bark whitish. The margin is not determinate. The photobiont is a species of the family Trentepohliaceae.
Fruitbodies
The apothecia are either emerging from the thallus or sitting on it with a broad base, and are irregularly rounded, shortly elongate or weakly lobed. They are brownish black, and sometimes have patches of a thin orange pruina. The apothecia are 0.1–0.5 mm in size and 70–140 μm tall. The disc is flat to slightly convex, and its surface is matt and rough.
The epithecium is 5–15 μm tall and colored reddish brown.
The hymenium is colorless and 45–90 μm tall.
The hypothecium is unpigmented or a pale brown, and 20–40 μm tall.
The paraphysoids are 1–2 μm wide. Their tips are widened to 2.5 µm, free, and with brown pigment deposited on the outer walls which occasionally form distinct caps.
The asci are globose to subglobose, 42–65 × 27–55 µm in size, and 8-spored.
The spores are colorless first, but turn brown with granular ornamentation when old. They are broad ellipsoid, 19–27 × 10–15 μm in size, and divided by 5–7 transverse septa and 1–4 longitudinal septa. An enlarged and undivided apical cell is not developed.
Anamorph
Pycnidia are unknown.
Chemistry
The thallus does not react with C, K, KC, Pd, or UV (C–, K–, KC–, Pd–, UV–). Lichen secondary compounds are not detected by TLC.
The hymenium reacts I+ red turning blue and KI+ deep blue. A KI+ blue ring structure has not been observed in the asci.
The brown pigment of the epithecium changes to greenish in K solution. Orange pigment granules, if present in the epithecium, dissolve with a purplish solution.
Arthothelium scandinavicum collected from a young Picea abies at Liåsen in Notodden (O-L-223602).
Ecology
Arthothelium scandinavicum is a rather common species on bark and wood of Norway spruce (Picea abies) in humid spruce forests in southern and southeastern Norway. Its distribution extends to Lierne municipality in northern Trøndelag. It is the only Norwegian Arthothelium species that preferably grows on Norway spruce (Picea abies). Literature reports indicate that A. scandinavicum is a species of mature to old-growth forests. North of Oslo, it is also frequently observed in younger spruce plantations.
Distribution in Norway and the Nordic countries
Arthothelium scandinavicum is an eastern species in Norway, being known from Kviteseid municipality in Vestfold and Telemark to Lierne municipality in Trøndelag. In the Nordic Countries, it is also known from Finland and Sweden.
Global distribution
Outside the Nordic Countries, Arthothelium scandinavicum is known from Estonia and Russia in Europe, and eastern Canada in North America.
Arthothelium scandinavicum collected from a young Picea abies at Dyplemyrnatten Ø in Hjartdal (O-L-223597).
Similar species
Arthothelium scandinavicum is a distinct species that cannot easily be confused with any other species in Norway. Felipes leucopellaeus may be superficially similar and also often grows on spruce in humid forests. That species differs by the more cobweb-like to minutely granular-powdery thallus and apothecia that are more clearly lobed, often characteristically depressed in the center, and lack an orange pruina. In most specimens, the apothecia are connected to the thallus by a thin layer or cobweb-like hyphae. The spores are much smaller, 10–17 × 3.5–5 µm, and transversely septate instead of muriform. The thallus contains the two Felipes unknown compounds.
Literature
Frisch A, Klepsland J, Palice Z, Bendiksby M, Tønsberg T and Holien H (2020). New and noteworthy lichens and lichenicolous fungi from Norway. Graphis Scripta 32(1): 1–47.
Sundin R (1999). Phylogenetic and taxonomic studies within Arthonia Ach. (Ascomycetes, Arthoniales). Doctoral dissertation, Department of Bot., Stockholm University.