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Lichen: Aspicilia calcarea

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Name: Aspicilia calcarea [(L.) Körb.]

Pronunciation: Aspicilia calcarea

Aspicilia calcarea on a bollard

Body Type: CrustoseAspicilia calcarea general view

Conservation Evaluation: Least Concern

Description:Apothecia The thallus is frequently very bright white, giving it the appearance of bird droppings, especially when seen on the top of walls. It may, however, also have off-white colours. The thallus has a cracked appearance similar to crazy-paving. The black apothecia are slightly depressed into the thallus and are frequently pruinose (covered in a white powder). They are irregular in shape. The thallus grows in a circular pattern. The edge or prothallus may be darker in colour and show radiating cracks. All specimens in Ireland have been found on calcareous rocks.

The photobiont is the unicellular green algae Trebouxioid. The apothecia are lecanorine. The top half of the paraphyses look like a string of beads. The spores (spherical or ellipsoidal) are colourless and single celled. The asci contain 4 to 8 spores.

Chemical Tests: K-.map-aspicilia-calcarea

Nature Notes: This is a common lichen on hard limestone and consequently is found on walls, gravestones and rocky outcrops, especially around lakes in the centre of Ireland. It is common along the river Shannon. It grows in a circular pattern at a rate of about 2.3 mm a year, but eventually settles down to 0.24 mm a year. Using these figures a specimen in England has been estimated to have started growing in 1195 AD. It current radius is 240 mm. It is a good source of food for snails, especially in limestone areas such as the Burren in Co. Clare.

Aspicilia calcarea is a saxicolous calcicole species.

Vice county distribution map of  Aspicilia calcarea: See Map.

Link: Map this species on the Lichen Survey

Other species recorded in Ireland

  • Aspicilia caesiocinerea (Nyl. ex Malbr.) Arnold
  • Aspicilia cinerea (L.) Körb.
  • Aspicilia contorta (Hoffm.) Kremp.
  • Aspicilia epiglypta (Norrl. ex Nyl.) Hue
  • Aspicilia grisea Arnold
  • Aspicilia intermutans (Nyl.) Arnold
  • Aspicilia laevata (Ach.) Arnold
  • Aspicilia leprosescens (Sandst.) Hav.
  • Aspicilia recedens (Taylor) Arnold
  • Aspicilia subdepressa auct.brit.

Text and images © Paul Whelan, 2009.