PARENT SESSION
Contributed Oral Session 85: Mutualism: Pollination
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal
Ecological costs and benefits of defenses in nectar.
Adler, Lynn*,1, Irwin, Rebecca2, 1 University of Massachusetts, Amherst, Amherst, MA2 Dartmouth College, Hanover, NH
ABSTRACT- The nectar of many plant species contains defensive compounds that have been hypothesized to benefit plants through a variety of mechanisms. Nectar attracts both pollinating and non-pollinating floral visitors, and plants may benefit from nectar traits that deter floral predators without also deterring pollinators. However, the relationship between nectar defenses and plant fitness has not been established for any species. We experimentally manipulated gelsemine, the principal alkaloid of Gelsemium sempervirens, in nectar to determine its effect on pollinator visitation, nectar robber visitation, and male and female plant reproduction. Gelsemium is a dioecious plant with a long-styled pin morph and a short-styled thrum morph. We experimentally augmented or diluted nectar alkaloids on plants in a field array in separate experiments over two years. We found that nectar robbers and most pollinators probed fewer flowers and spent less time per flower on plants with high compared to low nectar alkaloids. High alkaloids decreased the donation of fluorescent dye, an analog of pollen used to estimate male plant reproduction, to neighboring plants by one-third to one-half. However, nectar alkaloids did not affect female plant reproduction, measured as pollen receipt, fruit set, seed set, and seed mass. At natural concentrations, nectar alkaloids reduced fruit production on thrum but not pin plants. The lack of a consistent effect of nectar alkaloids on female reproduction might indicate that neither nectar robber nor pollinator visits affected female reproduction. Alternatively, the lack of an effect on female reproduction may represent a balance between the costs and benefits of altered nectar robber and pollinator behavior. Taken together, our results suggest that secondary compounds in nectar provide more costs than benefits to plant fitness.
Key words: toxic nectar, alkaloids, pollination, nectar robbing