FURTHER ANALYSIS OF OENOTHERA BIENNIS POPULATIONS FOR INCOMPATIBILITY ALLELES

The complex-heterozygotes of Oenothera biennis are characterized by an incompatibility allele system which acts as a part of the balanced lethal mechanism. A survey was made to determine the number and frequency of different incompatibility alleles in populations throughout south central Ohio and Indiana and in one population in northern Kentucky. No single population was found to possess more than two different alleles. Within the geographic area specified, however, at least eight different alleles occurred among the various population samples. If the incompatibility alleles are a valid index of variability for the complexes which carry them, these results suggest that individual populations are fairly uniform genetically and probably arise from relatively few colonizers. The various alleles found in these populations are believed to be relics of structurally homozygous self-incompatible progenitors which hybridized with structurally homozygous, but segmentally distinctive, self-compatible forms to give rise to the complex-heterozygotes.