EFFECTS OF A LOCUS AFFECTING FLORAL PIGMENTATION IN IPOMOEA-PURPUREA ON FEMALE FITNESS COMPONENTS

A locus influencing floral pigment intensity in the morning glory, Ipo moea purpurea, is polymorphic throughout the southeastern United State s. Previous work has suggested that the white allele at this locus has a transmission advantage during mating because of the effect of flowe r color on pollinator behavior. The experiment described here was desi gned to determine whether other effects of the W locus may contribute an opposing selective advantage to the dark allele. Dark homozygotes w ere vegetatively smaller and produced fewer flowers, seed capsules and seeds than either light heterozygotes or white homozygotes. In additi on, dark homozygotes produced smaller seeds than heterozygotes, and th ere is some indication that white homozygotes also produced smaller se eds than heterozygotes. Pleiotropic effects on seed number thus do not seem to contribute to selection opposing the mating advantage associa ted with the white allele. However, pleiotropic effects on seed size m ight contribute to overdominance that could stabilize the W locus poly morphism.