Genetics, Vol 132, 1195-1198, Copyright © 1992

INVESTIGATIONS

Heterozygote Advantage and the Evolution of a Dominant Diploid Phase

D. B. Goldstein
Department of Biological Sciences, Stanford University, Stanford, California 94305-5020

The life cycle of eukaryotic, sexual species is divided into haploid and diploid phases. In multicellular animals and seed plants, the diploid phase is dominant, and the haploid phase is reduced to one, or a very few cells, which are dependent on the diploid form. In other eukaryotic species, however, the haploid phase may dominate or the phases may be equally developed. Even though an alternation between haploid and diploid forms is fundamental to sexual reproduction in eukaryotes, relatively little is known about the evolutionary forces that influence the dominance of haploidy or diploidy. An obvious genetic factor that might result in selection for a dominant diploid phase is heterozygote advantage, since only the diploid phase can be heterozygous. In this paper, I analyze a model designed to determine whether heterozygote advantage could lead to the evolution of a dominant diploid phase. The main result is that heterozygote advantage can lead to an increase in the dominance of the diploid phase, but only if the diploid phase is already sufficiently dominant. Because the diploid phase is unlikely to be increased in organisms that are primarily haploid, I conclude that heterozygote advantage is not a sufficient explanation of the dominance of the diploid phase in higher plants and animals.

This article has been cited by other articles:

				D. W. Hall The Evolution of Haploid, Diploid and Polymorphic Haploid-Diploid Life Cycles: The Role of Meiotic Mutation Genetics, October 1, 2000; 156(2): 893 - 898. [Abstract] [Full Text]