Punctuated Evolution Induced by Ecological Change.

Despite the realization that common evolutionary patterns involve rapid morphological change, theoretical discussions of the ecological conditions necessary for such transitions are rare. An understanding of such conditions must be central to a reconciliation of the theories requiring novel mechanisms for punctuated evolution with theories based on population genetics. I develop an ecological context for evolutionary change of morphological characters important in resource use. The complexity observed in natural situations is reflected by a bimodal resource distribution. Intraspecific competition can produce rapid evolutionary change under these conditions. Furthermore, ecological situations that induce transitions can result from the species' foraging activities as well as from fluctuations in the environmental conditions. Thus, common ecological conditions coupled with well-known evolutionary processes can produce patterns observed in the paleontological record. [ABSTRACT FROM AUTHOR]