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Biology Articles » Biodiversity » Biodiversity in Africa » Species richness and endemism

Species richness and endemism
- Biodiversity in Africa

About 1,000 vertebrate species occur in just 4 of the 119 eco-regions (covering about 8 percent of Africa’s total area): Northern Acacia-Commiphora bushlands and thickets, Northern Congolian forest-savannah mosaic, Albertine Rift montane forests and Central Zambezian Miombo woodlands.

A quarter (1,229 species) of the world’s approximately 4,700 mammal species occur in Africa, including about 960 species in sub-Saharan Africa (SSA) and 137 species in Madagascar. The eastern and southern savannahs host large populations of mammals, including at least 79 species of antelope.

More than 2,000 bird species occur, constituting more than a fifth of the approximately 10,000 bird species in the world. About 1,600 bird species are endemic to SSA. Bird species richness is highest in Eastern Africa around the Albertine Rift montane forests, the Victoria basin forest-savannah mosaic, East African montane forests, Northern Congolian forest-savannah mosaic, and then into the Acacia-Commiphora bushlands and thickets and the Central Zambezian Miombo woodlands. The large size of these eco-regions, their high level of habitat heterogeneity, and their presence on a migratory flyway explain this pattern. The next highest band of species richness is found across the remainder of the tropical belt, with the exception of the western portion of the Upper Guinea forests and the centre of the Congo basin. The eco-regions of Madagascar and other offshore islands all have much lower bird species richness than the continental mainland.

Africa has about 950 amphibian species; however numerous new species and even genera are described every year. The highest levels of amphibian species richness occur in the DRC (210), Cameroon (189) and Tanzania (157); these countries are also ranked among the 20 countries with the highest level of diversity and endemism. The fauna of Madagascar are particularly undersampled: from 1990 to 1999 discoveries of new amphibian and reptile species increased the number of known species by 25 percent and 18 percent, respectively. The Congo basin is also under-represented due to inadequate surveys.

Overall plant richness at species, genus and family level is lower than that of other tropical areas. The African mainland has between 40,000 and 60,000 plant species, of which approximately 35,000 are endemic. South America, by comparison, has about 90,000 plant species in an area 40 percent smaller. Parts of the Congo basin have moderate levels of plant species richness, comparable to many parts of Central Europe. This is a consequence of major extinction events due to historic climate variations and fewer major tectonic events, which are thought to having triggered the evolution of many species in the South American Andes. Five of the 20 global centres of plant diversity are located in Africa. More than 3,000 plant species per 10,000 km2 occur in the Cameroon-Guinea centre, the Capensis centre, the Maputaland-Pondoland centre, the Albertine Rift centre and the Madagascar centre.

At least a sixth of the world’s estimated 270,000 plant species are endemic to Africa. The Cape Floral Kingdom, a global centre of plant endemism has about 9,000 vascular plant species occurring in an area of 90,000 km2 of which about 69 percent are endemic. More than 12,000 plant species occur in Madagascar, at least 81 percent of which are endemic, which is an exceptionally high proportion by global standards. More recent studies suggest that these figures for species richness and endemism in Madagascar may be underestimates.

Southern Africa has a rich and varied insect and arachnid fauna, with at least 580 families and about 100,000 species recorded. There is a high diversity of butterflies in the rainforests of the upper Guinea, the Albertine Rift, and the Congo basin, as well as in the Central Zambezian Miombo woodlands. Namibia is thought to be one of the global centres of arachnid richness and about one-third of the Southern African insect species are believed to occur in Namibia, although less than a quarter of these species are described.

Africa has several global centres of freshwater biodiversity and many of these are also centres of intensive fishing activity. Centres of species richness and endemism for freshwater fish, molluscs and crustacea are located in the upper Guinea river region (mainly Guinea and Liberia), Cabinda (DRC), and the eastern part of Madagascar. It is conservatively estimated that Africa has at least 2,000 fish species, which is thought to be the highest species richness in the world. The explosive diversification of certain types of fish, such as the Cichlidae in the Great Lakes, has contributed to this richness. Fish species richness in the Congo basin is second only to that of the Amazon basin. Data on endemism is inadequate. Fish diversity at the family level is somewhat lower than in southern America and Southeast Asia.

The coastal and marine ecosystems along Africa’s 40,000 km coastline contain a high marine biodiversity, with overlapping centres of endemism of, for example, fish, corals, snails and lobsters at the coast of eastern South Africa and in the Red Sea.

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