1. A burst of evolution, with rapid divergence from a single ancestral form, resulting in the exploitation of an array of habitats. The term is applied at many taxonomic levels, e.g. the radiation of the mammals at the base of the Cenozoic refers to orders, whereas the radiation of ‘Darwin’s finches’ in the Galápagos Islands resulted in a proliferation of species.
2. Term used synonymously with ‘cladogenesis’ by some authors.