Weekley, Carl W. , Brothers, Amanda .
Failure of Reproductive Assurance in the Chasmogamous Flowers of Polygala lewtonii (Polygalaceae), an Endangered Sandhill Herb.
Hypothetically, a species with both cleistogamous (CL) flowers and delayed selfing chasmogamous (CH) flowers should display high levels of reproductive assurance because, over time, obligate selfing by CL flowers should reduce inbreeding depression and delayed selfing in CH flowers should compensate for the absence of outcross pollen. We used pollinator-exclusion experiments to investigate reproductive assurance in the CH flowers of Polygala lewtonii, a perennial herb with a mixed mating system. We followed CH flowers from bud-break to flower/fruit abscission to quantify fruit initiation and maturation and rates of floral development. We also evaluated the efficacy of the selfing mechanism, conducted pollinator watches to assess the likelihood of pollinator limitation, and performed regression analysis to determine the effect of flower position on fruit production. We found that pollinator-exclusion significantly reduced fruit initiation and maturation. Investigation of floral development demonstrated that the selfing mechanism is dysfunctional in CH flowers, indicating the failure of reproductive assurance. Low observed rates of insect visitation appear to contradict high rates of CH fruit production in open-pollinated plants, particularly given the rarity of delayed selfing. In both treatments, flower position significantly affected fruit initiation, suggesting a possible role for resource limitation in both pollinator-excluded and open-pollinated flowers.
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1 - Archbold Biological Station, Plant Ecology Lab, P.O. Box 2057, Lake Placid, Florida, 33862, USA
2 - Indiana University, Department of Biology, Jordan Hall, 1001 East Third Street, Bloomington, Indiana, 47405, USA
Presentation Type: Oral Paper
Location: Salon F - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 8:30 AM