Pollination genetics of the common milkweed, asclepias syriaca L

Abstract

Electrophoretic methods are used to determine the genotype of individual pollinia simultaneously at several isozyme loci for the common milkweed, Asclepias syriaca. Isozymes of pollinia are the result of gene expression in pollen. Genotype frequencies of maternal plants, pollinia carried by honey bees and pollinia captured by flowers were determined and found to be comparable. Over 50% of bees carried genotypically mixed pollen loads. Methods for estimating the rate of selfpollination, assuming the mixed-pollination model, are developed and the rate of self-pollination in a population is found to be 66%. The use of the methods developed here for testing various hypotheses, including the operation of sexual selection in plant populations, is discussed. © The Genetical Society of Great Britain.