COll - Home of Arthonia atlantica

Did you know that Coll supports a large population of lowly but scientifically significant residents? Few people notice them, fewer still can name them, for their language is Latin. They were, however, given the closest attention and every one noted when a team of lichenologists came to Coll. The island is generally very rich in lichen, although a thousand years of agriculture, woodland destruction, peat cutting, muir burning and stock-rearing have all impoverished the lichen flora. Nevertheless the lichenologists had five fine field days here recording 410 varieties, a number of which were designated as 'rare' or 'very rare'.

Congenial conditions for lichens are produced on cliffs and gullies near the island coasts, with complex niche structure, small accumulations of windblown shell sand on ledges and crevices, and salt spray. Other habitats for lichen are found where low rock outcrops half buried in sand are present in the machair, allowing certain lichen flora to flourish among sharply drained ledges and spreads of moss. On Coll, the most natural macnair sites backing small isolated bays where a high density of lichens is found, are at Sorisdale and just east of A'Chroic. On bare sand at both these sites a species not described before was found. Ben Feall provides an important habitat, and sheltered gullies at Garbn Aird Beag have luxuriant lichen growths, including one rare variety. The sheltered shores of Loch Eatharna also support several varieties of lichen, and Coll's moorland acid rocks are covered with a close mosaic of them. Even rocks that are almost submerged in Loch Fada are clothed with lichen, with several kinds in a zone often wetted by waves.

The tree belt round the lodge, and the trees at the Garden House were found to be well covered with lichens, yielding 61 species for the record. The tiny fragment of older woodland on the south side of Loch Fada and the mossy rocks there added several more to the lichenologists' collection. Other rewarding sources were fence posts, stems of leggy heather, old bracken rhizomes and shreds of ivy where, in the absence of tree cover, many wood-growing species manage to survive.

Among the very rare varieties found on Coll, the Lichenologists recorded Arthonia atlantica, a newcomer to Scotland. Others were Aspicilia morioides; Candelaria concolor; Cladonia incressata; Lempholemma cIadodes; Placidiopsis custnanii and Polyblastia wheldonii. Important Coll residents indeed!

For this information we have to thank Dr Brian Coppins, Royal Botanic Garden, Edinburgh, and Or O. L. Gilbert, Depal1ment of Landscape Architecture, University of Sheffield.