Lichenen op hunebedden

The Dutch megalithic monuments, called ’hunebedden’, have been investigated for their lichen flora and vegetation in 1993-1994. They provide a unique environment for lichens in this country, because siliceous outcrops are absent otherwise. Many Red List species occur mostly or only on these boulders, including the nearly endemic Lecidea promixta. Many species are threatened by tourism or shading and some species are found to be extinct. Unexpected was the discovery of many usually corticolous species, such as Buellia griseovirens and Gyalideopsis anastomosans, and species reflecting the pollution by ammonia from manure, like Xanthoria polycarpa. Endococcus propinquus (Koerber) D. Hawksw., Fuscidea praeruptorum (Du Rietz & Magn.) Wirth & Vezda and Thelocarpon coccosporum Lettau were not previously reported from the Netherlands.