BackgroundThe disproportionate species richness of the world’s biodiversity hotspots could be explained by low extinction (the evolutionary “museum”) and/or high speciation (the “hot-bed”) models. We test these models using the largest of the species rich plant groups that characterise the botanically diverse Cape Floristic Region (CFR): the genus Erica L. We generate a novel phylogenetic hypothesis informed by nuclear and plastid DNA sequences of c. 60 % of the c. 800 Erica species (of which 690 are endemic to the CFR), and use this to estimate clade ages (using RELTIME; BEAST), net diversification rates (GEIGER), and shifts in rates of diversification in different areas (BAMM; MuSSE).ResultsThe diversity of Erica species in the CFR is the result of a single radiation within the last c. 15 million years. Compared to ancestral lineages in the Palearctic, the rate of speciation accelerated across Africa and Madagascar, with a further burst of speciation within the CFR that also exceeds the net diversification rates of other Cape clades.ConclusionsErica exemplifies the “hotbed” model of assemblage through recent speciation, implying that with the advent of the modern Cape a multitude of new niches opened and were successively occupied through local species diversification.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0764-3) contains supplementary material, which is available to authorized users.

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BackgroundThe coincidence of long distance dispersal (LDD) and biome shift is assumed to be the result of a multifaceted interplay between geographical distance and ecological suitability of source and sink areas. Here, we test the influence of these factors on the dispersal history of the flowering plant genus Erica (Ericaceae) across the Afrotemperate. We quantify similarity of Erica climate niches per biogeographic area using direct observations of species, and test various colonisation scenarios while estimating ancestral areas for the Erica clade using parametric biogeographic model testing.ResultsWe infer that the overall dispersal history of Erica across the Afrotemperate is the result of infrequent colonisation limited by geographic proximity and niche similarity. However, the Drakensberg Mountains represent a colonisation sink, rather than acting as a “stepping stone” between more distant and ecologically dissimilar Cape and Tropical African regions. Strikingly, the most dramatic examples of species radiations in Erica were the result of single unique dispersals over longer distances between ecologically dissimilar areas, contradicting the rule of phylogenetic biome conservatism.ConclusionsThese results highlight the roles of geographical and ecological distance in limiting LDD, but also the importance of rare biome shifts, in which a unique dispersal event fuels evolutionary radiation.