Geography of Iridaceae in Africa

Iridaceae, a family of worldwide distribution, comprises some 1 500 species and 85 genera. It exhibits its greatest radiation in Sub-Saharan Africa, where over half the species and some 48 genera occur. 45 of which are endemic. All three major subfamilial taxa are represented in Africa, where Ixioideae are almost entirely restricted, with extensions into Eurasia. Areas of greatest concentration are either montane or in areas of winter rainfall. In southern Africa alone, there are some 850 species in 46 genera, making the family the fifth largest in the flora. In the Cape Floristic Region there are 620 species, and the family is the fourth largest in this area. All major infrafamilial groups occur in the Cape Region where most of the variability as well as generic radiation is encountered. The idea of a southern origin for Iridaceae in Africa is analysed systematically, and is correlated with the major climatic changes that occurred in Africa since the mid-Tertiary, and culminated in the seasonally dry climates along the west coast. The establishment of mediterranean climate in the southwest provided the stimulus for massive speciation and radiation of the family there. Plio-Pleistocene uplift along the eastern half of the African continent led to the establishment of substantial upland areas and allowed the spread of some genera, such as Romulea, Gladiolus, Moraea, and Hesperantha into tropical Africa. Short-distance dispersal probably accounts for the presence of genera such as Gladiolus, Gynandriris and Romulea in Eurasia.

Abstract licence: CC BY

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