Island-matrix relationships in Nama Karoo inselberg landscapes - Part II: Are some inselbergs better sources than others?

To answer the question whether some inselbergs are better sources than others, thus potentially affecting processes in inselberg landscapes, inselberg-matrix affinities and the influence of regional physical environmental parameters (latitude, longitude, distance from coast and mainland) and parameters operating on landscape level (elevation and geology) were investigated. All investigated environmental parameters affected the observed patterns to some extend. Distance from mainland and geographic position were important on a regional level, while elevation only influenced the observed trends when investigated at a local level. Parameters determining better sources within the selected study areas and sites, here simply defined as showing higher floristic affinities with the surrounding, appeared to be inselbergs: (a) in southern Namibia and thus in an inland position; (b) at a distance from other mountainous habitats; and (c) of low elevation. Although the importance of inselbergs for conservation and maintenance of biodiversity is evident, this study points towards a complex situation, ruling out the sole effect of any one of the parameters investigated at regional and landscape level. Further observations and analysis at a local level may give some pointers and assist in identifying critical aspects important for conservation and range management.