MULTISPECIES COMPETITION IN VARIABLE ENVIRONMENTS

A general model of competition between several species in a variable e nvironment is presented and analyzed using a general method that unifi es treatment of different specific models. This method yields broad co nclusions that are independent of the details of a model. It is used h ere to show that mechanisms of coexistence and competitive exclusion a re largely restricted to three broad categories. One of these categori es includes classical mechanisms that do not depend on fluctuations ov er time. Another category includes mechanisms which may be referred to collectively as the storage effect. These mechanisms involve species- specific responses to environmental fluctuations, a relationship betwe en fluctuations in competition and fluctuations in the environment, an d an interaction between environment and competition. The final catego ry depends on fluctuating competition and nonlinear responses to compe tition that differ between species. These general results are illustra ted with analyses of several specific models, including a Lotka-Volter ra model, a model of nonlinear resource consumption, and models of rec ruitment fluctuations for iteroparous organisms and for annual plants. (C) 1994 Academic Press, Inc.