Parmelia acetabulum

The B.L.S.

Current names - Synonyms - Key - Habitat lists (either Current names or Synonyms) - Chemistry lists (either Current names or Synonyms) - Glossary

982 : Parmelia acetabulum (Necker) Duby

Pleurosticta acetabulum

British and Irish distribution
Markedly eastern distribution in Britain, extending N. into NE. Scotland; still frequent in SE. England, S. Midlands, E. Anglia and Kent. Rarer and more scattered elsewhere; absent W. of Somerset, apart for a few localities in Wales; exterminated by pollution in parts of W. Midlands and much of Yorkshire; good example of a continental distribution in Britain.

Substrate ecology
On nutrient-rich bark of Acer spp., Fraxinus, Aesculus, Ulmus (formerly), etc., in well-lit open sunny parklands, meadows or roadsides; rarely on neutral sandstone-ragstone gravestones and church walls. Mainly confined to areas of low rainfall (<800 mm) where organic nutrient-rich dust tends to settle on the trunks.

Phytosociology/associated species
A member of the Xanthorion alliance, particularly the Physcietum adscendentis association: usually with Physcia (sensu lato), Ramalina and Xanthoria spp., Diploicia canescens, etc. Never in woodland communities.

Status
Native and still widespread in the SE., but much reduced in N. Midlands and N. England, probably by air pollution; adversely affected by inorganic fertilizers, especially in wayside hedgerows, and much rarer in arable areas than 50 years ago.

Conservation
Tolerates SO₂ levels up to c. 60 µg m^-3; will probably increase now in areas where SO₂ levels have fallen, but the death of most mature Ulmus has caused serious reductions in abundance. Much grazed by molluscs, which may even limit its spread into wetter regions.

World distribution
Widespread in C. and S. Europe, from C. Sweden to N. Africa; rarer in W. Europe, but commoner to S. and E. where it occurs in forest situations, even on Abies in montane forests; probably endemic to Europe and N. Africa.

Identification
The wrinkled, grey to olive-green thallus (bright oily green when wet), lack of isidia and soralia, and the usual presence of large (to 1cm) crenulate, cup-like apothecia, are distinctive features; medulla K+ blood-red (crystals).

Observations
Usually fertile, unless poorly developed.

References
Purvis, O. W. et al. (1992) p. 436; Maas Geesteranus, R. A. (1941) Blumea 6: 100-106; Wirth, V. (1987) p. 315; Brightman, F. H. et al. (1973) Lichenologist 5: 476-477; Seaward, M. R. D. & Hitch, C. J. B. (1982) map 89.