PARENT SESSION
Oral Session #31: Plant Reproductive Ecology, Pollination, and Dispersal. Presiding: J. Karron.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Hall of Ideas L&M.
The influence of floral display size on mating patterns in Mimulus ringens.
KARRON, JEFFREY1, MITCHELL, RANDALL2, HOLMQUIST, KARSTEN1, BELL, JOHN1, 1 2
ABSTRACT- The number of flowers blooming simultaneously on a self-fertile plant may have profound consequences for reproductive success. For example, plants with large displays may receive more pollinator visits, increasing seed production. However, large displays may also entail significant costs. For example, self-pollination is much more likely, since large displays promote within-plant pollinator movements. If there is inbreeding depression, female reproductive success will suffer. Self-pollination may also decrease pollen transfer to other plants, reducing male reproductive success. This project utilizes a novel experimental system to test the hypothesis that these conflicting selection pressures favor the evolution of intermediate-sized floral displays. We manipulated monkeyflower (Mimulus ringens) floral displays in replicate (cloned) populations consisting of individuals with distinct multilocus genotypes that facilitate unambiguous measures of paternity and individual selfing rates. As predicted, the fraction of moves between flowers on the same plant increased with display size (from 10% for two-flower displays to over 71% for 16-flower displays), greatly increasing the opportunity for self-pollination on plants with large floral displays. Genetic analysis confirms that this change in pollinator behavior also increases rates of self-pollination for large floral displays. Patterns of pollinator movement also varied among three species of bumble bees, indicating that they may differ in the quality of pollinator service they provide.
KEY WORDS: MATING SYSTEM, SCROPHULARIACEAE, SELF-POLLINATION, POLLEN