Origin and diversification of African ferns with special emphasis on Polypodiaceaele

Although Africa harbors low species diversity compared to the neotropics or South East Asia, the African fern flora is of interest because of its specific composition and geographic location between the neotropics and Asia. We address the question of how the evolution of the African fern flora may have been enriched by repeated input from the neotropics and Asia. For the purpose of this paper we consider three major biogeographic regions: the neotropics, Africa and Madagascar, and Asia including Malesia and Australasia. We interpret distribution data for six clades of Polypodiaceae in a molecular phylogenetic framework. We conclude that African fern taxa shared with or closely related to ones in the neotropics or Asia have been brought about by ancient and recent dispersal events with or without subsequent speciation. The African fern flora is interpreted as being composed of endemic, neotropical, and Asian elements and as being situated in a zone of overlap of typical neotropical and Asian fern floras.