Rare lichen tufts on Shiants are world's most northerly
The world's most northerly tufts of a rare lichen have been recorded on a group of small Hebridean islands, according to Scottish Natural Heritage.
Lichenologists discovered the golden-hair lichen on the Shiant Islands four miles (6km) off the coast of Lewis.
The lichen belongs to the genus Teloschistes, which means "split ends" and is classified as vulnerable in Great Britain.
SNH said the lichen had not been seen in Scotland since the 1830s.
It was last recorded in Scotland on Ailsa Craig in the Firth of Clyde.
Once found across Britain, colonies of golden-hair lichen have been trimmed back to a few coastal sites in south-west England and western Wales.
The lichen is extremely sensitive to sulphur dioxide air pollution.
Crofters on Lewis use the Shiants for grazing sheep.
The islands also provide habitat for more than 150,000 birds, including 10% of the UK's puffin population.
A project to wipe out non-native black rats from the Shiants to protect the seabirds was awarded almost £450,000 of European Union funding last year.
The rats are the descendents of rats thought to have come ashore from shipwrecks in the 1900s.