Cape flora

The Cape province of South Africa is considered a continental ' hotspot' with a rich diversity of species of flora. In the July 12 Nature, Richardson et al., from the Royal Botanic Gardens in Richmond, UK, report the results of a molecular phylogenetic analysis that dates the era of speciation to about 7-8 million years ago (Nature 2001, 412:181-182). They sequenced nuclear ribosomal and plastid DNA from island species of the buckthorn Phylica, as well as continental species from the Cape, and constructed a series of phylogentic trees. The dispersal of one species from Mauritius to the Reunion island 2 million years ago provided an internal calibration for their molecular clock, and the related Nesiota genus from St Helena island (14.3 million years old) served as an external reference. Richardson et al. conclude that the species diversification took place around 7-8 million years ago. Thus, explosive speciation on continents appears to progress over the same timescale as on island archipelagos. The authors suggest that understanding the process of biodiversity is essential if conservation programmes are to be successful.