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Rapid and recent origin of species richness in the Cape flora of South Africa

Abstract

The Cape flora of South Africa grows in a continental area with many diverse and endemic species1,2,3,4. We need to understand the evolutionary origins and ages of such ‘hotspots’ to conserve them effectively5. In volcanic islands the timing of diversification can be precisely measured with potassium–argon dating. In contrast, the history of these continental species is based upon an incomplete fossil record and relatively imprecise isotopic palaeotemperature signatures. Here we use molecular phylogenetics and precise dating of two island species within the same clade as the continental taxa to show recent speciation in a species-rich genus characteristic of the Cape flora. The results indicate that diversification began approximately 7–8 Myr ago, coincident with extensive aridification caused by changes in ocean currents. The recent origin of endemic species diversity in the Cape flora shows that large continental bursts of speciation can occur rapidly over timescales comparable to those previously associated with oceanic island radiations6,7.

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Figure 1: One of the six phylogenetic trees.
Figure 2: Histograms of bootstrap results using two different nodes to calibrate the molecular clock for Phylica.

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Acknowledgements

We are grateful to P. Crane, M. Sanderson and the Tropical Biology Group at the Royal Botanic Garden, Edinburgh, for critical comments and discussion. We thank A. de Bruijn and J. Joseph for technical support. The work was funded by a studentship to J.E.R. from the Royal Botanic Gardens, Kew, which also made possible a four-month visit by F.M.W. to Kew to collect additional data. We also thank collectors of plant material: Y. Mungroo, C. Thébaud, M. van der Bank and R. Cairns-Wicks.

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Correspondence to James E. Richardson.

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Richardson, J., Weitz, F., Fay, M. et al. Rapid and recent origin of species richness in the Cape flora of South Africa. Nature 412, 181–183 (2001). https://doi.org/10.1038/35084067

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