Taxonomic, Edaphic and Biological Aspects of Narrow Plant Endemism on Matched Sites in Mediterranean South Africa and Australia

This paper analyses the edaphic and biological aspects of plant endemism in floristic lists from five edaphically matched sites, and the taxonomic aspects in regional Boras, from the Agulhas Plain, South Africa and the Barrens, south western Australia. The two regions are very closely matched in terms of their mediterranean-type climates, landforms, soil types and disturbance regimes. Both regions have large neo-endemic floras. At the Bora level, the incidence of local and regional endemism was almost identical on both continents (c. 6% and 22%, respectively) and endemics were not a random assemblage taxonomically. Endemics were over-represented among taxa speciose only in Australia (e. g. Myrtaceae) and only in South Africa (e,g. Mesembryanthemaceae), as well as among taxa richly represented on both continents (Proteaceae, Ericaceae/Epacridaceae). In both regions different edaphic sites supported Boristically distinct sclerophyllous shrublands. Levels of narrow endemism on the various substrata were similar on both continents, ranging from near zero on the relatively fertile calcareous sands to 30% on the highly infertile quartzites and siliceous sands. Relative to Australia, however, endemics on limestone were significantly over-represented in South Africa. On both continents more than 90% of endemics were edaphic specialists. There were differences for the two regions in the biological profiles of endemics. South African endemics were most likely to be low shrubs with soil-stored and ant-dispersed seed. Australian endemics were concentrated among low to medium height shrubs with either canopy-stored or soil-stored seed. Differential diversification of lineages with different ecological traits probably accounts for these different profiles. Nonetheless, the strong overall similarities in patterns of endemism on the two continents suggests similar speciation histories in phylogenetically distantly related Boras