The Maintenance of Single-locus Polymorphism. V. Sex-dependent Viabilities

Abstract

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 (se...