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Arthonia ilicina Taylor

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Tornflekklav.
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Arthonia ilicina (Norway)

Arthonia ilicina grows on smooth bark of deciduous trees in the boreo-nemoral rainforests in Rogaland and Vestland. It is characterized by brownish black rounded to shortly elongated apothecia on a whitish to cream-yellow thallus with trentepohlioid photobiont. The spores are pale brown and finely warted, 5–6(–7)-transversely septa and have an enlarged apical cell.

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Arthonia ilicina collected from Tilia cordata in a boreo-nemoral rainforest at Øvrabø Ø in Stord (O-L-226300).

Description

Thallus

The thallus is white to cream-yellow. It is continuous, immersed in the host bark, and has a smooth, matt to weakly glossy surface. The margin is either not determinate or more often bordered by a distinct brown line. The photobiont is a species of the family Trentepohliaceae.

Fruitbodies

The apothecia are level with the thallus surface or indistinctly raised. They are irregularly rounded, elliptical or shortly elongated, brownish black in color, and without pruina. They are 0.2–1 mm in size and 90–130 μm tall. The disc is flat to slightly convex.

The epithecium is brown to red-brown and 20–25 μm tall.

The hymenium is colorless to yellowish brown and 60–85 μm tall.

The hypothecium is colorless to yellowish brown and up to 30 μm tall.

The paraphysoids are ca 1 μm wide. Their tips are slightly widened to 1.5–2 µm. The tips are predominantly upright and with brown pigmented walls.

The asci are clavate, 55–70 × 24–30 µm in size, and 8-spored.

The spores are thick-walled, colorless first, with a pale brown pigmentation and finely granular ornamentation when old. They are obovoid, often slightly bent, 25–36 × 9–13 μm in size, and divided by 5–6(–7) transverse septa. The apical cell is enlarged.

Anamorph

Pycnidia are sparse, dark brown, either immersed in the thallus or slightly raised, and 60–80 µm in size. The wall is red-brown in color. The rod-shaped conidia are 7–9.5 × ca 1 μm in size.

Chemistry

The thallus does not react with C, K, KC, Pd or UV (C–, K–, KC–, Pd–, UV–). Lichen secondary compounds have not been detected by TLC.  

The hymenium reacts I+ blue (the epithecium often later I+ red) and KI+ blue. A KI+ blue ring structure has been observed in the asci.

The brown pigment in the epithecium and the wall of the pycnidia changes to greenish in K solution.

Tornflekklav.
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Arthonia ilicina collected from Fraxinus excelsior at Hatledalsåsen in Bjørnafjorden (O-L-226325).

Ecology

Arthonia ilicina is confined in Norway to the boreo-nemoral rainforests. It often occurs in rather open, Scots pine (Pinus sylvestris) dominated forests with a high proportion of deciduous trees. Arthonia ilicina often grows on thin stems and branches with sparse lichen cover and may be a weak pioneer species. Common hazel (Corylus avellana), holly (Ilex aquifolium) and rowan (Sorbus aucuparia) are common host trees, but the species is also reported from European ash (Fraxinus excelsior) and goat willow (Salix caprea).

Distribution in Norway and the Nordic countries

Arthonia ilicina is distributed in Norway throughout the core area of the boreo-nemoral rainforests from Stavanger in the South to Kinn municipality in the North. In the Nordic countries, the species is further reported from the west coast of Jutland, Denmark.

Global distribution

Outside the Nordic Countries, Arthonia ilicina is known from the British Islands to Portugal and the Mediterranean in coastal Europe, the Canary Islands, Madeira, North America, South Africa and Australasia.  

Tornflekklav.
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Arthonia ilicina collected from Ilex aquifoliium in a boreo-nemoral rainforest at Sylvikehaugane in Stord (O-L-224334).

Similar species

Arthonia ilicinella differs by smaller ascospores that are 16–23 × 7–9 μm in size and have 3–4 (–5) transverse septa, and by generally smaller apothecia. This species is not yet reported for Norway.

From superficially similar Arthothelium species growing in the boreo-nemoral rainforests, like A. dictyosporum and A. macounii, Arthonia ilicina can be separated most easily by its transversely septate instead of muriform spores.  

Nettsporeflekklav.
Arthothelium dictyosporum (Coppins & P. James) Coppins
Hasselflekklav.
Arthothelium macounii (G. Merr.) W.J.Noble

Remarks

Literature

Cannon P, Ertz D, Frisch A, Aptroot A, Chambers S, Coppins BJ, Sanderson N, Simkin J and Wolseley P (2020). Arthoniales: Arthoniaceae. Revisions of British and Irish Lichens 1: 1–48.

Christensen SN, Alstrup V and Svane S (1995). Floristic notes from SW Denmark. Graphis Scripta 7(2): 87–89.

Coppins BJ and James PW (1979). New or interesting British lichens III. Lichenologist 11: 27–45.

Czarnota P, Guttová A, Halda J, Kukwa M, Liška J, Palice Z, Peksa O, Svoboda D and Vondrák J (2006). Lichens recorded during 13th Spring Meeting of the Bryological and Lichenological Section CBS on an excursion to the Tematínske vrchy hills (Považský Inovec. Mts., Slovakia). Bryonora 38: 26–39.

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.

Ihlen PG and Coppins BJ (1999). Two species of Arthothelium (Arthoniaceae, Arthoniales) new to Scandinavia. Nova Hedwigia 69(3–4): 391–397.

Sundin R (1999). Phylogenetic and taxonomic studies within Arthonia Ach. (Ascomycetes, Arthoniales). Doctoral dissertation, Department of Bot., Stockholm University.