Arthothelium macounii

Taxon

Arthothelium macounii

Authority
(G. Merr.) W.J. Noble (1987)
Synonyms
Arthothelium ilicinum var. reagens
Arthothelium reagans
Conservation Status
VU D2 NR P Sc IR (Key)
BLS Number
96
Taxon Photo
Arthothelium macounii, on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll
Arthothelium macounii, on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll
Arthothelium macounii, apothecia cross section in water, on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll
Arthothelium macounii, apothecia cross section in K, on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll
Arthothelium macounii, spores in K, on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll
Arthothelium macounii, spores in K, on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll
Arthonia cohabitans (small dark flecks), on Arthothelium macounii (larger dark flecks on dark thallus), on Hazel in Atlantic Hazel wood, Ballachuan, Seil, Argyll © The Trustees of the Natural History Museum, London, CC BY 4.0 fromhttps://www.gbif.org/occurrence/1056256306
General Description

A special and rare species of the best Atlantic Hazel woods with large Arthonia type apothecia with a brownish purple tinge on a brown-grey to fawn thallus. Spores large with with a undivided enlarged apical cell and apothecial sections K+ purple-violet or magenta, see the similar A. dictyosporum.

Identification

Like A. dictyosporum, but apothecia with a brownish purple tinge; thallus around the apothecia often reddish orange; epithecium purplish, K+ purple-violet; epithecium, hymenium and hypothecium with orange-red oily inclusions that are K+ magenta. Ascospores 20–38 × 10–14 µm, with a undivided enlarged apical cell and the lower part with 4–6 transverse septa and at maturity most transverse cells with 1 or 2 longitudinal septa, when old brown and distinctly warted.

Sometimes parasitised by Arthonia cohabitans.

Habitats

On smooth bark of Hazel, rarely Ash, in old Atlantic Hazel woods in the core area of temperate rainforest in the western Highlands, Mull and Skye

Distribution Map
Arthothelium macounii 10km sq distribution map
Arthothelium macounii 10km sq distribution map
Key to map date classes
Distribution

Rare, W. Scotland (Argyll to Skye).

Threats & Status

A rare species of high quality Atlantic Hazel woods, with threats from both under grazing and over grazing.

Britain: Vulnerable & International Responsibility species.

Scotland: Priority Taxon for Biodiversity in Scotland.

References

Cannon, P., Ertz, D., Frisch, A., Aptroot, A., Chambers, S., Coppins, B. J., Sanderson, N. A., Simkin, J. & Wolseley, P. (2020) Arthoniales: Arthoniaceae, including the genera Arthonia, Arthothelium, Briancoppinsia,Bryostigma, Coniocarpon, Diarthonis, Inoderma, Naevia, Pachnolepia, Reichlingia, Snippocia, Sporodophoron, Synarthonia and Tylophoron. Revisions of British and Irish Lichens 1: 1 - 48

Text by Neil A Sanderson, based on Cannon et al (2020)

Lichenicolous Fungi
Arthonia cohabitans Coppins (1989)