Biodiversity & Conservation

, Volume 5, Issue 5, pp 551–573

Why is the Cape Peninsula so rich in plant species? An analysis of the independent diversity components

  • M. T. Simmons
  • R. M. Cowling

DOI: 10.1007/BF00137609

Cite this article as:
Simmons, M.T. & Cowling, R.M. Biodivers Conserv (1996) 5: 551. doi:10.1007/BF00137609


With 2285 species of higher plants crammed into 471 km2, the flora of South Africa's Cape Peninsula is exceptionally rich. Similar sized areas in other Mediterranean-climate region biodiversity hot-spots support between 4.7 and 2.7 times fewer species. The high plant species richness of the Cape Peninsula is due to the exceptionally high turnover between moderately species-rich sites in different habitats (beta diversity) and between sites in similar habitats along geographical gradients (gamma diversity). Highest beta diversity, encompassing almost complete turnover, was recorded along soil fertility gradients. Although similar patterns for these independent components explain the richness of other regions in the Cape Floristic Region, it is the very long and steep habitat gradients of the Cape Peninsula that makes this region exceptionally rich. Furthermore, the flora is characterized by a high degree of rarity, a phenomenon that undoubtedly influences the turnover. Future research should focus on developing a biological and ecological understanding of the different forms of rarity and integrating this into management plans for the maintenance of biodiversity.


alpha diversitybeta diversitygamma diversityfynbosrarity

Copyright information

© Chapman & Hall 1996

Authors and Affiliations

  • M. T. Simmons
    • 1
  • R. M. Cowling
    • 1
  1. 1.Institute for Plant Conservation, Botany DepartmentUniversity of Cape TownRondeboschSouth Africa