Protein polymorphism and genic heterozygosity in a population of the permanent translocation heterozygote, Oenothera biennis.

Genic allozyme polymorphism and heterozygosity was studied in a large population of the evening primrose, Oenothera biennis, growing in North Haven, Connecticut. This species is a permanent structural heterozygote for the entire complement of 14 chromosomes, and is thus capable of accumulating and maintaining genic heterozygosity. A total of 11 protein species were examined, and these were judged to be controlled by 19 loci. Polymorphism occurs at 26% of the loci, with only two alleles being present at each locus. The proportion of polymorphic loci per population in organisms with normal meiotic systems is no less than in Oe. biennis, indicating that structural heterozygosity is not necessarily accompanied by a greater proportion of polymorphic loci. On the other hand, the average Oe. biennis was heterozygous at 26% of its loci, an amount considerably greater than in most other organisms. With few exceptions, all plants in the North Haven population had the same genotype. Since the species is a colonizer, it is likely that the population was founded by a single individual and retained this genotype by virtue of the genetic system.