Diversity of Rock‐Inhabiting Cyanobacterial Lichens: Studies on Granite Inselbergs along the Orinoco and in Guyana

Abstract

Abstract: A survey was undertaken of specialized saxicolous cyanobacterial lichens growing on exposed granitic rock surfaces of inselbergs in Venezuela and additionally in Guyana and French Guyana. The study focused on taxonomy and species composition. Twenty‐three cyanobacterial lichens were found, four of which are new to science: Peltula auriculata, Phylliscum vermiformis, Psorotichia polyspora and Pterygiopsis guyanensis. Besides the new species, almost all taxa are absent from the available lists of lichen‐forming fungi from the Guyana region. Although free‐living cyanobacteria are the dominant group in biological crusts covering the inselbergs, the number of cyanobacterial lichens is relatively high and their distribution is homogenous over long distances and macro‐climatic gradients. As inselberg rock faces undergo relatively fast weathering under moist tropical climates, numerous micro‐habitats are formed. Among these, xeric micro‐habitats are favourable for colonization by cyanobacterial lichens, mainly of the Lichinaceae and Peltulaceae. It is concluded that granite inselbergs in the savannas of the Orinoco lowland and the Guyana region are local centres of diversity for saxicolous cyanobacterial lichens.