Multiple interactions: An empirically suggested model

A modified version of Schoener's non-linear competition model is presented. The model describes the competitive dynamics of two species competing for a common resource. A second resource made available by species 1 for the exclusive use of species 2 is also present. This second resource is generated in an undefined way from the common resource. The presence of the exclusive resource serves to prevent the extinction of species 2 even when that species is at a great competitive disadvantage in obtaining the common resource. A feedback loop is established, dependent on the exclusive resource, making possible an increase in numbers of species 2 as the numbers of species 1 increase. This is represented as a reversal in the slope of the species 2 isocline. The behavior of the isoclines of both species is examined as certain key parameters are varied. The model is related to the results obtained from experiments involving Tribolium and Drosophila.