EVOLUTIONARY CHANGES OF ECOLOGICAL TRAITS OF BACTERIAL-POPULATIONS THROUGH PREDATOR-MEDIATED COMPETITION .2. THEORETICAL CONSIDERATIONS

A causal mechanism of replacement of variants in a prey population through predator-mediated competition was investigated using a mathematical model, and experimental results obtained in an accompanying paper were explained. The model shows that an increase in intrinsic growth rate and/or a decrease in predation rate of prey can increase predator equilibrium density, at least under some conditions, which in turn causes negative growth rate of previous types of prey. It is also indicated that the predator's responses in density due to changes of the prey traits can be affected by trade-offs between two parameters of the prey, intrinsic growth rate and predation rate. These mathematical results can explain qualitative aspects of the experimental results.