Rock outcrop communities usually receive very little attention from scientists and environmentalists. We examined the vegetation occurring in eight gneiss-granite rock outcrops at Rio de Janeiro State (Brazilian Atlantic coast) which exists in natural associations on soil islands. A total of 86 vascular plant species, belonging to 30 families, was found on 347 soil islands. Bromeliaceae, Asteraceae and Velloziaceae species were the most frequent plants, many of them endemic to these habitats. Ordination and cluster analyses using species frequency on each site made evident some major distinctions related to local influences, most probably the proximity to the sea. Each outcrop presented high values of the Shannon-Wiener index of species diversity. Species richness was very dependent on the total area, and high beta diversity was observed amongst sites. Similarities with the South American and African rock-outcrop communities were found. Despite their uniqueness as habitats, their possession of several endemic species and the fragility of the ecosystem involved, Brazilian rock outcrops are not protected by specific environmental legislation and we propose urgent actions for their protection.

Inselbergs are rounded rock outcrops, usually of Precambrian age, with sparse vegetation cover. The vegetation of inselbergs in Zimbabwe is described for the first time, based upon data sampled from 53 localities. Inselbergs support a range of habitats whose vegetation is described. Data on species richness and floristic composition of the inselberg flora (549 vascular plant, 25 bryophyte and 136 lichen species) are presented. Phytogeography and diversity of inselberg vegetation are discussed. First records for Zimbabwe are reported in lichens and vascular plants.