Adaptive Radiation

Adaptive radiation is a term used to describe a period in evolutionary history when a single or a few species diversified and underwent relatively rapid speciation. The event is distinguished from the background pattern of evolution in two ways: in pace and in the extent of diversification. These deviations from the slow and gradual flow of evolution are “adaptive” in that they are driven by natural selection as new species expand into vacant ecological niches. They are “radiation” events in that they result in expansion of the taxonomic group from one or a few to several or many species.

This rapid speciation is often accompanied by an increase in extinction rates as well, because not all the initial emergent forms are successful. For example, if one ...