Predator Evolution in a Model of Interacting Species: To the Question about Maintaining Polymorphism by Litter Size in Natural Populations of Arctic Fox.

We propose an ecogenetic model of "prey–predator" community with predator fitness determined genetically by a single autosomal diallelic pleiotropic locus in the case of diploid population. Predator genotypes with different reproductive potential are unequally adapted to food resource limitation; therefore, the fitness of a predator's genotype is determined by not only its own genotype but also the prey numbers. We use discrete-time equations for modeling, which allows considering features of the community species lifecycle. The paper extends our previous studies modeling evolution of a local population to explain existing genetic diversity by litter size in various (natural and farmed) populations of Arctic foxes (Alopex lagopus). Direct inclusion of prey population dynamics in the model of community allows analyzing polymorphism maintenance in arctic fox populations under more realistic conditions. As in simpler models, the direction of evolution of the predator population is shown to be generally determined by the relative position of its genotype fitnesses, whereas the parameter set characterizing birth rates of the prey and the predator, as well as the characteristics of interspecific interaction, determines the dynamic mode of interacting species numbers. However, even without overdominance, a predator can maintain a stable polymorphism owing to large-amplitude fluctuations in the number of prey, which change the direction of natural selection in the predator population. Different dynamics in the genetic composition of the predator can lead to a change in the dynamic mode of the prey numbers. [ABSTRACT FROM AUTHOR]