Evolution of the Carnivorous Adaptive Zone in South America

Abstract

The role assumed by an animal group in a community is best understood when the structure of the community is viewed in historical perspective (MacArthur, 1972; Pianka, 1974). In many environments it is not physiological and behavioral limitations which guide a group’s evolutionary strategy, but the opportunity to exploit available adaptive zones, which because of the nature of the fauna, were vacated (Hecht, 1975:248). It is often assumed or implied that a particular systematic group can, in its adaptive radiation, fill all the available niches within a particular adaptive zone (Hecht, 1975:247). The type of analysis of a “taxocene” (Whittaker, 1972:218) which promotes these views has obvious shortcomings. It is now evident that mammals, for example, were unable to equally exploit and partition available adaptive zones on every continent. The failure of mammals to do this to a complete degree in Australia (see Hecht, 1975:247) and in South America (see below) has some historical basis in the development of the stratification of the vertebrate fauna.