A Adaptive Radiation

Adaptive radiation is one of the most important outcomes of the process of evolution, and islands are places where it is best observed. The term itself was fi rst used by H. F. Osborn in  in describing parallel adaptations and convergence of species groups on different land masses. Since then, adaptive radiation has been widely recognized and defi ned in multiple ways to emphasize the contribution of key features thought to underlie the phenomenon, including adaptive change, speciation within a monophyletic lineage, and time. Dolph Schluter, a prominent researcher in the fi eld, defi nes it as “the evolution of ecological diversity within a rapidly multiplying lineage.” There are radiations that are not adaptive. These are mostly caused by changes in topography that, instead of opening up new habitats, have served simply to isolate a previously more widespread species. Island radiations are likely to include adaptive as well as non-adaptive evolutionary elements. In this article, the focus is on adaptive evolutionary radiations.