Since natural selection requires variation to act, the amount of genetic variation in a given population is of central theoretical and experimental importance. This amount is estimated by the genetic variationpresent in current popu- lations. Electrophoretic studies of natural populations reveal that ten to twenty percent of all loci have multiple al- leles. These multi-allelic loci may be the result of the accumulation of unselected mutations (neutral theory) or of balancing selection (selectionist theory). The neutral theory views selection as primarily eliminating variation, whereas the selectionist theory views selection as often maintaining variation. Therefore, our view of selection and evolution depends upon the question of how multiple allelic systems evolve. To address whether balancing selection increases genetic variation, we examined Owen™s model in which se- lection varies in the two sexes (sex-dependent model) and compared it to a model in which selection is constant across the two sexes (sex-independent model). We explored these models for a single multi-allelic locus to explore more generally the effect of balancing selection on the maintenance and construction of multi-allelic systems. To do so, we constructed two computer models. The ihfitness-spacel. approach examines the proportion of all possible fitnesses capable of maintaining different sized allelic systems. The proportion of possible fitnesses is greater in balancing selection models. The ihconstructionistl approach examines the ease in reaching this portion of possible fitnesses. The ease in reaching fitnesses is less in balancing selection models. Thus, in contrast to previous hypoth- eses, our research suggests that balancing selection may not increase the amount of variation present in natural populations.
Bodmer, W. F. (1965): Differential fertility in population genetics models. Genetics51:411-424.
'Differential fertility in population genetics models' () 51Genetics: 411-424.
Differential fertility in population genetics modelsGenetics51411424)| false