Diversification in the genus Striga.
Forty taxa are admitted in the genus Striga, and in this paper a list of species is proposed with synonyms. The occurrence of Striga taxa in 11 defined regions (or sub-continents) was studied, and it was found that 82.5% of the taxa occur in Africa, with the number of species decreasing gradually through Asia, from Arabia to Indomalaysia and Australia. A number of species exhibit morphological or biological characters considered unusual in the genus, thus expressing generic variability and diversity. The number of endemic species in each of the 11 regions was compared to the regional representation of the genus, and to the genus as a whole. Of the Striga species occurring in Africa, 78.8% were endemic to the continent and the highest rate of endemism was found in the W. and central region, where 14 endemic taxa represented 35% of the whole genus. In conclusion, it is confirmed that primary diversification occurred in Africa, with the genus probably extending from Africa to Asia. The main diversification centre of the genus seems to be located in W. and central Africa and a secondary diversification centre may be recognized in Australia. The diversification of the genus is possibly a recent phenomenon.