In a first step to investigate the potential source-sink function of isolated mountains (i.e. inselbergs) in an arid landscape, affinities of inselberg floras with their surrounding were investigated in four sets of inselbergs in Namibia's Nama Karoo. The questions focussed on (a) the potential of inselbergs to serve as sources for degraded rangelands, and (b) the role of species attributes in the relationship between inselberg and matrix. The study showed that inselbergs can serve as source for degraded rangeland, but at regional and landscape level employed in this analysis, the species attributes growth form and seed dispersal did not provide any conclusive trends. Keywords: arid environment, growth form, Island biogeography, Namib desert, seed disperal, source-sink function, southern Africa.