Cyprinids of Africa

Abstract

Africa straddles the tropics and contains a wide range of biotopes from rain forests to major deserts. Temperate climates occur only in the extreme south and in restricted zones ofhigh altitude. The western half ofthe continent is weil watered within tropicallatitudes. but rainfall is seasonal in the north. east and south. Dry desert or semi-desert conditions prevail in the north and to the south-west. On a broad scale the continentallandscape comprises an elevated plateau impressed with the basins ofmajor drainages ofthe Nile, Niger, Zaire, Zambezi and the Orange (Roberts, 1975; Beadle, 1981). The palaeohistorical view is that some of these basins were formerly major areas of endorheic drainage, possibly forming immense inland lakes that were later captured by encroaching coastal systems (Beadle, 1981). There are few extant large endorheic drainages in Africa, but Lake Chad and the Okavango basins are notable examples. The Great Lakes of Central and East Africa are prominent features and their faunal histories are closely interwoven with the geomor-phological evolution of the East African Rift system. Drainage evolution throughout Africa is intricately associated with the distribution patterns of freshwater fishes. About ten African ichthyofaunal provinces are recognized (Roberts, 1975) (Fig. 7.1). Although they are not strict biogeographical units (Greenwood, 1983), they are useful entities for discussing regional patterns of fish distribution. Roberts (1975) partitioned Africa into low and high sectors. high Africa lying to the south and east of a line drawn from the north of the Ethiopian highlands, down and around the rim of the Zaire basin to the Atlantic coast off Angola. The riverine fish faunas of high Africa are relatively poor and domina ted by the cyprinids. Those of low Africa include the species-rich Guinean, Zairean and Nilo-Sudanic faunas and include many archaic and phyletically isolated groups such as the polypterids, notopterids. and large proportions of certain anotophysans (e.g. Kneriidae).