Address: * Corresponding author. Email aldasoro at ma.rjb.csic.es

Aim This paper reports the diversity and end endemism patterns of African ferns, and explores the potential role of diversity refuges and environmental factors in the shaping of these patterns.

Material and locations The extant fern taxa occupying Africa south of the Sahara, Madagascar and some islands of the South Atlantic.

Methods The number of taxa in each area or operational geographical unit (OGU) was scored, and the correlation between this number and physical and climatic variables analysed by standard pairwise and stepwise multiple regression analysis (SPR and SMR). The effects of biological factors such as dispersal capacity, reproductive biology, genetic features and certain physiological adaptations were evaluated by comparing the number of species in each OGU. Floral affinities among OGUs were analysed using non-metric multi-dimensional scaling (NMS) and parsimonic analysis of dispersion (PAD), and compared with β-turnover and inter-OGU distances.

Results OGU area, elevation and the distance between refuges determined the composition of local floras, but only greater OGU area and the existence of higher maximum elevations increased species richness.  The distance between refuges also effected the number of endemic species, especially on islands. The biological features studied only slightly influenced fern distribution. The main clinatic predictor of species number was humidity. SPR and SMR revealed three groups of ferns with different ecological trends. NMS and PAD analyses separated the four areas of highest diversity n Africa, three of which are inhabited byferns with distinct ecological requirements. The fourth area was Madagascra, which shows an accumulation of endemic and relict diversity that is not easy to explain.

Main conclusions The distribution of ferns in Africa has been influenced by refuges. These probably allowed many species to recolonize the neighbouring areas after the extinctions of the Pleistocene. Three main components were dtected in the African flora: Guinea-Congolian thermophilous, cold-tolerant Afro-montane, and Southern drought-tolerant elements. These are related to the three main refuge areas, i.e. the Gulf of Guinea area, the eastern tropical region, and the Cape region. Endemicity in ferns was found to be lower than that of seed plants due to the higher dispersability of fern spores. The distance between OGUs seems to be the main predictor of the number of endemic fern species these areas contain.

Journal of Biogeography 2004. 31: 1579-1604.