Floristic biodiversity and history of African arid regions

The phytochorological patterns of the arid flora of Africa are discussed on various levels. The arid regions of the African continent are linked by a large number of taxa with disjunct distribution. Analysis of these disjunct patterns supports the hypothesis of fragmentation of a once continuous arid belt running from the Namib desert region to the Western Sahara via East Africa. The flora of the arid regions of Southern Africa shows regular patterns, e.g. identical fragmentation of distribution areas of several taxa on an infrafamilial or infrageneric level, allowing formulation of a hypothesis concerning the sequence of differentiation steps during formation of the floras. Very interesting patterns can be attributed to effects of the last glaciation. For example, disjunct distribution patterns in the Namib region can be interpreted as a result of survival of palaeotropical taxa in warm refuge areas during the last glaciation.