The role of Namibian inselbergs in contributing to local and regional plant species richness

Abstract

This study investigated four inselberg landscapes in Namibia's arid Nama Karoo. Inselbergs of different size and geology were investigated (a) to determine environmental variables influencing the number of inselberg restricted plant species and (b) to investigate seed dispersal spectra as one parameter describing functional properties of inselberg specialists. With regard to the role of inselbergs in contributing to local and regional species richness, many species restricted to inselberg habitats occurred (up to 79 species recorded in this survey) and so contribute to local and regional species richness. As no species endemic to an inselberg were recorded in this study, inselberg specialists may provide an indicator for conservation value of these mountains. Elevation rather than surface area provided a measure for predicting the number of inselberg specialists. Besides elevation, underlying geology, and resulting landforms and edaphic conditions, as well as distance to potential mainland also influenced the number of inselberg specialists. Functional relationships between inselbergs based on seed dispersal spectra of inselberg specialists were not conclusive.