The occurrence of 23 cyanobacterial species, belonging to 9 different
genera and 5 cyanobacterial lichen species of 5 different genera on ex
posed, open rock surfaces of inselbergs and on soil in savannas of the
Orinoco lowlands and the Guayana uplands is described. Their distribu
tion patterns and frequency within the different habitats are given. T
he filamentous procaryotic blue-green algae/cyanobacteria Stigonema oc
ellatum and Scytonema crassum, together with the unicellular cyanobact
erium Gloeocapsa sanguinea were the most frequent species on rocks, wh
ereas the filamentous cyanobacterium, Schizothriz telephoroides, domin
ated in cyanobacterial mats on the savanna soil. All species showed in
tensively coloured sheaths, either brown or yellow in the case of Stig
onema ocellatum and Scytonema crassum, or red in Gloeocapsa sanguinea
and Schizothrix telephoroides. In addition, a number of cyanobacterial
lichens occurred.