Most biodiversity studies have focused on the extremely rich tropical regions of the Earth.  Twenty percent of the world's plant species occur in the five warm temperate Mediterranean climate regions, many of which are endemic.

HOTSPOT ANALYSIS

Myers defined it as areas characterized by high species richness, high concentrations of endemic species and which are experiencing high rates of habitat modification or loss.

Initially Myers identified 10 hot spots, all of which were in the tropical rainforest.  He then extended his hot spot analysis to include additional Rain Forests and four Mediterranean-climate regions including the Cape Floristic Region (CFR).

There are a total of 18 hot spots which comprise 50 000 species.  The Cape Floristic Region has over 6 000 endemic species and emerged as the "hottest" of the world's hotspots.

DEFINITION: Flora South African (FSA) extends south of the Kunene and Limpopo rivers and comprises 21 137 specie sof vascular plant, 80% of which are endemic.

Plant endemism is not distributed evenly across South Africa

This is summary of the following paper: 

Cowling, R.M. & Hilton-Taylor (1994) Patterns of plant diversity and endemism in southern Africa: an overview. In Botanical Diversity in Southern Africa (ed Huntley, B.J.) Strelitzia 1: 31-52 

This paper has five main aims, namely:

• To compare the species richness and endemism in the Flora of Southern Africa (FSA) with other areas of the world.
• To identify hot spots of plant diversity and endemism within the FSA.
• To determine whether the hot spot endemics have any special characteristics.
• To describe the major threats to the FSA.
• To propose methods of ensuring the conservation of plant resources.

BIODIVERSITY IN THE FLORA OF SOUTHERN AFRICA (FSA)

There are 23 404 taxa plus infraspecific taxa of vascular plant

Species richness is higher than 8 of the 12 "Megadiversity countries"; namely Australia, Ecuador, India, Indonesia, Madagascar, Malaysia, Peru and Zaire.

In contrast to the above countries FSA is predominantly warm-temperate and semi-arid region with a mean annual rainfall of 400 mm.  The amount and seasonality of rainfall does vary considerably over southern Africa,.

Table 1 Vascular plant species density in southern Africa and similar sized regions of the world.

Another difference between FSA and other floristically rich areas is the lack of species rich tropical rainforest regions (forest cover less than 1% of the FSA)

The FSA's rich biodiversity is attributable to a transitional position with respect to subtropical summer rainfall and temperate rainfall regimes in combination with complex topography and heterogeneity of geology and soils.  These circumstances produce many steep ecological gradients along which species can partition themselves.

FSA has been divided into

• 5 phytochoria
• 7 biomes
• 70 major vegetaton categories or veld types (Acocks)
• 68 vgetaton typesidentified by Low & Rebelo

Historical processes have also contributed to the regions biodiversity.

ENDEMISM

The endemism of vascular plants in southern Africa is exceptionally high, and more like what you expect on an oceanic island.

Attributable to diverse ecological conditions are
Product of high speciation within genera (species to genus ratio is 9.6) and parallelsthe product of adaptive radiation occurring on oceanic islands.

Genera with many species are mostly found in Fynbos and Succulent Karoo biomes.

Compared to global flora the southern African flora comprises a distinct phylogenetic sequence.

The southern African flora contains most of the world's species of Mesembryanthemumaceae, Ericaceae, Aizoacea, Amaryllidaceae, Iridaceae, Restionaceae as well as high proportions of Geraniaceae, Proteaceae and Rutaceae.

The southern African flora has 13 endemic or near endemic families.

Most of the endemic families are monogeneric and almost all are restricted to the winter rainfall regions.

SOUTHERN AFRICAN HOTSPOTS

Biodiversity is not evenly distributed e.g. CFR covering 3.5% of the region has 41% of the species.

Seven centres of palnt diversity have been identified in southern Africa

Ranges in endemism based on the IUCN centre of plant diversity project and range from 4% to 68% which comapres with tropical rainforest of 44%

The Cape with 6000 endemic species is the hottest hot spot and the Succulent Karoo with 1600 endemic species is the semi-arid area that is also a global hot spot.

8830 endemic species and exceptionally high species to genus ratios of southern Africa is one of the most important areas for conservation action.

CHARACTERIZATION OF THE ENDEMIC FLORA

An analysis of the floras reveal distinct floras, three hot spots are analyzed below:

AUGULHAS PLAIN - dominated by endemics belonging to Ericaceae, Restionaceae and Proteaceae

NATAL DRAKENSBERG - Asteraceae, Scrophulariaceae and Ericaceae

GARIEP - Mesembryanthemum, Crassulaceae, Asclepiadaceae

Generally found that the taxonomic aspects of endemism show greater differences than similarities across the three hot spots.  The same families have different proportions of endemics in each region.

BIOLOGICAL ASPECTS

• Endemism with respect to biological aspects are different across the southern African hotspots
• Endemic forbs are common in moist summer rainfall eastern hot-spots.
• Endemic shrubs are common to all hot-spots.
• Endemic geophytes and succulents are common in semi-arid southwest
• Endemic trees are rare except in Maputaland and Pondoland

CONSERVATION STATUS

• The protected area network in South Africa is not optimally located with respect to hot-spot regions, plant diversity and endemism.
• Reasonably large conservation areas exist for Wolkberg and Maputaland.  Mountain areas of the Cape are well conserved.
• The succulent Karoo is desperately poor as isthe lowlands of the Cape Floristic region.

Conserved areas and number of Red Data Book (RDB) taxa in southern African hot-spots

Major threats to southern African hot-spots