In flowering plants reproductive success is measured not only by the number of seeds produced in an individual's own fruits, but also by the number of seeds sired in fruits of other plants. This second component of reproduction has been coined, " male reproductive success," because it reflects a plant's ability to disperse pollen or male gametes to other receptive individuals in the population. Few studies have measured male reproductive success in natural plant populations. Consequently, we know very little about the characteristics that make certain individuals more successful male parents than others. This issue is central to our understanding of the evolution of floral traits and functional sex ratios in plant populations. The proposed research will use protein markers (isoenzymes) to monitor paternity in experimental populations of the alpine plant, Polemonium viscosum. In this way it can be determined whether male reproductive success is influenced by extensive variation in flower size, pollen production and nectar production in this species. The proposed research has important implications for crop improvement and management. First, our ability to prevent contamination of crop seed by pollen of related weed populations depends on our knowledge of factors controlling pollen donation. Next, spread of valuable genetic improvements through crop populations can be accomplished most readily if genes for such improvements are associated with others enhancing paternal success. Third, introducing superior pollen donors into stands of orchard or seed crops should improve yield with little economic cost and no environmental damage. The proposed research will provide information basic to reaching these goals.
