© 1979 by The Society for Integrative and Comparative Biology
Recombination in a Simulated Predator-Prey Interaction
Department of Ecology and Evolutionary Biology, Division of Biological Sciences, University of Michigan Ann Arbor, Michigan 48109
The influence of a co-evolved predator-prey interaction on the outcome of competition between sexual and asexual prey was examined by computer simulation. Intraspecific competition in both predator and prey populations is governed by relative success in the interspecific interaction. Predators key on a certain variable prey character under the control often independently assorting, diploid loci. Individual predators vary genetically in their ability to handle prey of the various states of this character. Predator fitness is proportional to the prey available to them. Prey fitness is inversely proportional to the frequency of predators to which they are susceptible. In addition, sexual prey of a given phenotype are assigned half the fitness of the corresponding asexual form, representing a "cost of meiosis." Mating is random and there is no facultative response allowed to changes in the phenotypic distribution of the interacting species. Three parameters are varied: (1) the maximum contribution of a phenotype to the next generation (fecundity limit), (2) population size, and (3) clonal diversity of the asexual prey form. Most realistic combinations of these variables favor sexual reproduction. According to the model, it is particularly unlikely that an asexual mutant could spread in an existing sexual population. However, the conditions found to favor asexuality are consistent with observations from nature where reduced recombination is relatively common. The model predicts asexual forms should persist in very large, low fecund populations, as in the prokaryotes, and where their phenotypic diversity is high, as near zones of recurrent hybridization. It is also consistent with the occurrence of parthenoforms in regions of reduced interspecific interaction where the assumptions of this model, and therefore the advantages to sex, are less likely to be realized.