Concentration of Dominance and Adaptive Zones

Abstract

Ecologists have long recognized that temperate communities generally exhibit a characteristic pattern of species abundances few species boasting many individuals and relatively many species each represented by few individuals (Fisher et al. 1943). This phenomenon of concentration of dominance (generally regarded as the inverse of species diversity) is obviously characteristic of many natural communities. Because of its ubiquity, however, the classic J-shaped distribution may reasonably be expected to be of some evolutionary significance. Thus, Gause (1936) considered the quantitative relation between the numbers of rare and abundant species to be the most important aspect of a community's structure. Hutchinson (1953) commented is likely that something very important is involved here and then added, (significantly) but for the present what it may be is a mystery. In addition, Williams (1964) has reported numerous instances of equivalent concentration of dominance among animal taxa, generally revealing a species (represented by many individuals) with many relatively rare congenors. It thus appears that the Jshaped pattern goes beyond community structure in its relevance, reflecting something in the taxonomic as well as local ecologic affinities of organisms. Further, this distribution also appears among higher taxonomic categories, where many large taxa reveal a dominant sub-taxon (considering number of species rather than