Lichen (Caloplaca aractina)

Caloplaca aractina
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Lichen fact file

Lichen description


Caloplaca aractina is a 'crustose' lichen; one with a crusty-like appearance. The body of the lichen (its thallus) is an oily dark brown to grey colour, which means it can be overlooked against the rock on which it grows. The fruiting bodies are slightly more obvious when they appear, being orangey-brown in colour, sometimes bright red though very small (less than 1mm).

Patch diameter: several cm.

Lichen biology

Lichens have colonised some very extreme habitats, including some of the coldest and hottest areas of the planet. They are incredibly hardy organisms, able to survive for years on the minimum of water, and growing almost imperceptibly slowly. If you examine the colonies that grow on tombstones, you can work out the age of some of these patches of lichen. Tombstones usually have a date on them revealing the year that the bare stone became available for colonisation.


Lichen range

In the UK, the range of this lichen is limited to the Lizard Peninsular, Cornwall where it is quite frequent on coastal rocks. There are other records from the British Isles but these are now believed to be incorrect. It is also found along the coasts of western Europe and from inland southern Europe.

You can view distribution information for this species at the National Biodiversity Network Gateway.

Lichen habitat

This lichen likes sloping rocks, up to 100 metres above high water mark. On the Lizard Peninsular, it is always on serpentine rock. Elsewhere, it seems to prefer silica-rich rocks.


Lichen status

Classified as Critically Endangered in the UK.


Lichen threats

This species is not currently threatened, though it may be vulnerable to oil spill incidents on some of its sites. It is not fully understood why this species has declined so drastically over the last fifty years. Scrub encroachment might prove a threat at its only known site in the UK.


Lichen conservation

Caloplaca aractina is listed in the UK Biodiversity Action Plans and included in English Nature's Species Recovery Programme. The site on the Lizard where it is found is a National Nature Reserve, so appropriate management for the species does not pose a problem. However, with a species that has such a precarious status in Britain, it is important to find out as much as possible about its requirements. It is necessary, too, to make mycologists (fungi experts) aware of this species and encourage them to report any sightings of the lichen elsewhere. Part of the Species Action Plan for C. aractina is to compile a list of suitable sites to search for the lichen, and compile a database of endangered lichens. This might help other members of this fascinating group that are critically endangered.

There may be further information about this species available via the National Biodiversity Network Gateway.
The UK Biodiversity Action Plan for this species is available at UK BAP.


Information supplied by English Nature.



Type of simple plant body that does not have stems, leaves and roots.



Image credit

Caloplaca aractina  
Caloplaca aractina

© Frank Dobson

Frank Dobson
57 Acacia Grove
New Malden
United Kingdom
Tel: +44 (0) 208 949 2416
Fax: +44 (0) 208 949 2416


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