Evidence for radiations of cheilanthoid ferns in the Greater Cape Floristic Region

The Greater Cape Floristic Region (GCFR) of southern Africa is characterised by large, endemic radiations of flowering plants, the so-called 'Cape Clades', but it is unknown whether such radiations are also found in non-angiosperms. We hypothesise that GCFR-endemic lineages exist in the xeric adapted cheilanthoid terns. To test this hypothesis with special emphasis on the alternative hypothesis of frequent colonization, the phylogenetic relations, divergence times, and ancestral areas of the cheilanthoid ferns of the GCFR and adjacent regions are investigated. The dataset includes 22 cheilanthoid fern species occurring in the GCFR. With two exceptions, all GCFR-endemics are part of two clades that diversified in the Afro-Madagascan region. The GCFR-endemics are further concentrated in three high-endemism subclades that did not originate simultaneously, but within the timeframe of angiosperm Cape Clades diversification. According to ancestral area reconstructions the ancestors of the two larger Afro-Madagascan clades were likely GCFR-endemic, and a substantial part of the diversification history of these clades took place in the GCFR. The high diversity of cheilanthoids in the GCFR appears to stem primarily from in situ diversification, not from immigration. This pattern resembles the numerous radiations of angiosperm clades in the GCFR, and may be caused by the same factors. We did not find evidence for rapid, synchronised radiations as documented for some, albeit not all, angiosperm Cape Clades. High diversification within and dispersal out of the GCFR has likely enriched cheilanthoid diversity in the Afro-Madagascan region.