The Carbonicola anthracophila, which only grows on charred conifer trees, was discovered by scientists surveying Loch Arkaig Pine Forest near Spean Bridge.
The lichen has only been recorded at three other locations in the UK: Glen Affric, Glen Quoich and Glen Strathfarrar, all in Scotland.
The latest discovery has been recognised as a “living legacy” of Second World War Commando training.
British Commandos and Allied Special Forces including the Free French trained at Loch Arkaig during the conflict. During exercises with live ammunition in 1942, forest fire raged across the hillside. Scots pines cooked in their own resin were preserved and still stand like ghost trees across the hillside.
Now, some 77 years on, the rare fire lichen is thriving as a result of the blaze.
Woodland Trust Scotland bought Loch Arkaig Pine Forest in partnership with local group Arkaig Community Forest at the end of 2016, with support from players of People’s Postcode Lottery.
Experts Andy Acton and Brian Coppins were commissioned to carry out the lichen survey to help inform long term conservation management at the site. The four-day survey found around 150 different species. In their report the experts said they had only scratched the surface of what the forest might hold. The Carbonicola anthracophila was found on just two tree stumps.
Mr Acton said today/yesterday [FRI] the rare species enthusiasts were excited to “tick off” the lichen following its discovery, adding: “It was the first time I had seen this particular species so it was particularly exciting for me, but Brian referred to it as a ‘mega tick’ so he was clearly excited too.
“Brian found it first, then the hunt was on for more and I went on to find it on another stump.”
Loch Arkaig was the location for a sequence in Harry Potter and the Deathly Hallows. Harry, Hermione and Ron cling to a dragon as it flies above the forest before jumping off into the Loch below. Filming on the shore is thought to have been cut short because the midges were too fierce.
The forest is also home to wild boar, sea eagles, golden eagles, ospreys, pine martens and deer amongst many other species.
Steeped in history, a consignment of gold sent from France to help fund the escape of Bonnie Prince Charlie in the 18th century is said to be hidden in the forest.
Woodland Trust Scotland has partnered with Arkaig Community Forest, a local community-based charity, to help achieve ambitious long-term goals for the 1027-hectare site.