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Arthonia excipienda (Nyl.) Leight.

Forrige Opp Neste
Kantflekklav.
Creative Commons Attribution Share-alike | Andreas Frisch

Arthonia excipienda collected from a dead Viburnum opulus at Anggårdan NØ in Nesna (O-L-206473).

Arthonia excipienda is a pioneer species on smooth bark of deciduous trees in humid forests and woodlands. It is known in coastal Norway north to Leka in Nordland. Arthonia excipienda is characterized by brownish black, lirellate apothecia with a well-defined margin and slit-like apothecial disc, an indistinct thallus lacking photobionts. The colorless spores are 1-septate.

Description

Thallus

The thallus is thin and indistinct. The margin is either not determinate or bordered by a thin brown line. Photobionts are absent.

Fruitbodies

The apothecia are lirellate, brown-black, and without pruina. They are straight, bent or wavy in shape, simple or sometimes branched, and raised over the thallus. They are 0.2–1.5 × 0.1–0.2 mm in size, and 40–100 μm tall. The margin is often raised over the narrow, slit-like disc.

The exciple is well-defined, 12–60 µm thick and reddish brown in color.

The epithecium is 5–25 µm tall and pale brown or pale olive-brown.

The hymenium is unpigmented and 30–60 μm tall.

The hypothecium is unpigmented and up to 15 μm tall.

The paraphysoids are 1–1.5 μm wide. Their tips not widened and without distinct pigment caps and plaques.

The asci are broadly obovoid, without stipe, 24–45 × 20–26 µm in size, and 8-spored.

The spores are colorless, obovoid, 12–18 × 4–7 μm in size, and divided by 1 transverse septum. The apical cell is not enlarged.

Anamorph

Pycnidia are not reported for the species.

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+ red and KI+ blue. A KI+ blue ring structure has been observed in the asci.

The brown pigment in the apothecia changes to pale green in K solution.

Kantflekklav.
Creative Commons Attribution Share-alike | Andreas Frisch

Arthonia excipienda collected from Fraxinus excelsior at Øysteseelva in Kvam (O-L-222352).

Ecology

Arthonia excipienda is a pioneer species of humid forests and woodlands in coastal Norway including riverine forests and the boreo-nemoral rainforests. It grows on smooth bark of deciduous trees and is often found on thin stems and branches. Host trees observed in Norway include common hazel (Corylus avellana), European ash (Fraxinus excelsior), European barberry (Berberis vulgaris) and guelder-rose (Viburnum opulus). The species is further reported in the Nordic countries from alder (Alnus spp.) and spurge laurel (Daphne mezereum). 

Distribution in Norway and the Nordic countries

Arthonia excipienda is known from scattered localities in coastal Norway from Oslo in the South to Leka in Nordland. In the Nordic countries, it is further known from Finland and southern Sweden.

Global distribution

Outside the Nordic Countries, A. excipienda is confirmed from western Europe including the British Islands, Italy, and the Alps. Most records of A. excipienda are old and the species appears to be extremely rare outside the Nordic countries and the British Islands.

Kantflekklav.
Creative Commons Attribution Share-alike | Andreas Frisch

Arthonia excipienda collected from Nyveien in Holmestrand (O-L-148222).

Similar species

Occasional specimens of Naevia punctiformis with narrow, long elongated apothecia differ from A. excipieda by larger spores, 14–25 × 5–9 μm in size and with 3 to 5 transverse septa. The apothecia lack a well-defined margin and slit-like disc. The hymenium reacts I+ blue (or blue mixed with red).

Naevia dispersa has smaller spores, 9–15 × 3–5 μm in size, a I+ blue hymenium and lacks a well-defined apothecial margin and slit-like disc.

Kvistflekklav.
Naevia punctiformis (Ach.) Beltr.
Dvergflekklav.
Naevia dispersa (Schrad.) Thiyagaraja, Lücking & K.D.Hyde

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.

Sundin R (1999). Phylogenetic and taxonomic studies within Arthonia Ach. (Ascomycetes, Arthoniales). Botaniska institutionen, Stockholms universitet, Stockholm.

Wirth V, Hauck M and Schultz M (2013). Die Flechten Deutschlands, vol. 1+2. Ulmer, Stuttgart. 1244s.