Present address: Department of Philosophy and Religious Studies, Iowa State University, Ames, Iowa, 50011-1306, USA.
Effects of variation at the flower-colour A locus on mating system parameters in Ipomoea purpurea
Article first published online: 27 APR 2004
Volume 13, Issue 7, pages 1839–1847, July 2004
How to Cite
Fehr, C. and Rausher, M. D. (2004), Effects of variation at the flower-colour A locus on mating system parameters in Ipomoea purpurea. Molecular Ecology, 13: 1839–1847. doi: 10.1111/j.1365-294X.2004.02182.x
- Issue published online: 27 APR 2004
- Article first published online: 27 APR 2004
- Received 10 December 2003; revision received 13 February 2004; accepted 13 February 2004
- anthocyanin genes;
- male reproductive success;
- mating systems;
- population genetics;
Although alleles at both the W and A loci in the common morning glory, Ipomoea purpurea, produce similar white-flowered phenotypes, these alleles differ by over an order of magnitude in average frequency. In this initial attempt to determine the causes of this difference, we employed artificial arrays of plants to estimate mating system characteristics (total siring success, selfing rates and contribution to the outcross pollen pool) for the homozygous pigmented and white-flowered genotypes at the A locus. This experiment demonstrates that: (1) at both low and high frequencies, white-flowered plants were visited by pollinators at the same rate as plants with pigmented flowers; (2) at both frequencies, the a allele exhibited a greater total siring success (self and outcross pollen) than the A allele; (3) individuals of both genotypes contributed equally to the outcross pollen pool; and (4) aa plants may have a higher selfing rate than AA plants. Coupled with minimal inbreeding depression in I. purpurea, these observations indicate that the allele producing white flowers enjoys a transmission advantage that would tend to cause this allele to increase in frequency. This transmission advantage is very similar to that shown previously to be operating on the white-flowered allele at the W locus, although the specific causes of the advantage appear to differ between loci. The frequency difference between the two alleles is thus not likely to be due to differences in the effect of flower-colour variation on transmission. Rather, substantially greater deleterious pleiotropic effects associated with the white-flower a allele is likely to be the primary cause of the frequency difference.