Coevolution in Predator-Prey Systems: A Saturation Kinetic Model

A saturation-kinetic model has been used to study coevolution in predator-prey systems. In a series of computer simulation experiments, we have examined the genetic and ecological consequences of genetically determined variability in efficiency of predation (measured in terms of half-saturation constants). Examples are presented in which seemingly erratic changes in population size may be simply explained on the basis of underlying (deterministic) changes in genetic structure. It has been shown that in other cases considerable genetic change is possible with relatively little effect on population sizes. We have specified conditions under which it is possible to maintain stable cycles of population sizes and/or gene frequencies in both predator and prey even though the half-saturation constants, as well as all other input variables, remain constant through time. The model suggests a mechanism whereby a predator population can use evolutionary change as a "genetic tracking" device following changes in prey composition.