TAXON:	Phaeophyscia orbicularis (Neck.) Moberg (1977)
RECENT SYNONYMS:	–
FAMILY:	Physciaceae
GROWTH FORM:	Foliose, heteromerous
SUBSTRATES:	Any nutrient-rich or eutrophicated substrate whether bark, worked wood or stone; hard, calcareous artificial substrates such as concrete, cement, etc
PHOTOBIONT:	Trebouxioid alga
REPRODUCTION:	Soredia; apothecia occasional; pycnidia frequent
ASCUS:	If present, cylindric-clavate; apex Lecanora-type; 8 spores
SPORES:	Ascospores if present ellipsoidal, brown, 1-septate, thick-walled, distoseptate, 17-26 × 7-11 µm; conidia if present ellipsoidal
NOTABLE FEATURES:	Thallus greenish-gray to brownish-green, usually orbicular; lobes closely adpressed, typically broad and overlapping but sometimes narrow and discrete; underside black; rhizines dark and unbranched, often projecting beyond lobe ends like used old brush, and paler where projecting; soralia mostly laminal, usually convex but sometimes flatter and abraded, often with ‘creamy’ appearance
CHEMICAL TESTS:	All negative, or occasionally K+ purple where cortex shows yellow-orange patches (skyrin)
HABITAT:	Wherever suitable substrate available, including urban areas
DISTRIBUTION:	Common and widespread in Britain
CONSERVATION STATUS:	Least Concern
LICHENICOLOUS FUNGI:	Arthonia phaeophysciae, Athelia arachnoidea, Buelliella physciicola, Erythricium aurantiacum, Illosporiopsis christiansenii, Laeviomyces fallaciosus, Lichenochora obscuroides, Monodictys cellulosa, Paranectria oropensis, Sclerococcum phaeophysciae, Taeniolella phaeophysciae, Tremella phaeophysciae
IDENTIFICATION DIFFICULTY:	Green 1: Field identification possible
CONFUSION SPECIES:	Hyperphyscia adglutinata, Physcia caesia

FIELD NOTES

Phaeophyscia orbicularis finds the modern British environment very much to its liking. This nitrophilic lichen isn’t picky about substrate so long as it’s nutrient-rich. In rural areas where excess nutrients from agriculture have enriched many surfaces, you’ll find it on bark, worked wood or stone. In urban areas, where dusts and vehicle exhaust have done the same, you’ll find it on pavements, wall cappings and copings, street-trees and the like. No doubt it’s somewhere near you!

P. orbicularis isn’t hard to identify. In its typical form, it takes a distinctive ‘orbicular’ or circular shape composed of more-or-less overlapping green-gray or green-brown lobes, and studded with little mound-like soralia that become paler and ‘creamy-looking’ when eroded. But at first glance it can be confused with Hyperphyscia adglutinata or Physcia caesia, and particularly the former if the thallus happens to be small.

It’s fairly easy, though, to confirm that you have P. orbicularis. Many differences exist between these three lichens, but the clearest of them are usually the following:

• P. orbicularis is somewhat more loosely attached to the substrate than H. adglutinata, whose lobes are often surprisingly hard to peel back.
• The underside of P. orbicularis is dark, while those of H. adglutinata and Physcia caesia are pale.
• Unlike Physcia caesia, P. orbicularis lacks atranorin, and it doesn’t test K+ yellow.
• Unlike either of the other lichens, P. orbicularis often sports rhizines that extend beyond the edges of its lobes, giving it the look of a used old brush.

The last of these characteristics may be absent from some specimens. But in general you’ll find them reliable, and you’re very likely to be able to find and recognise P. orbicularis near you if you go looking for it.

LAB NOTES

Phaeophyscia orbicularis can normally be identified without microscopy.

SPECIMENS

Phaeophyscia orbicularis : England : VC26 West Suffolk : TM0540 : May 2025 : On fallen Fraxinus branch

Phaeophyscia orbicularis : England : VC20 Hertfordshire : TL3510 : March 2025 : On wooden bench

Phaeophyscia orbicularis : England : VC27 East Norfolk : TG0738 : October 2024 : On derelict metal culvert

Phaeophyscia orbicularis : England : VC25 East Suffolk : TM3389 : April 2024 : On concrete pavement