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 Mimulus ringens floral display size on patterns of pollinator visitation.
MITCHELL, RANDALL1, KARRON, JEFFREY2, HOLMQUIST, KARSTEN2, BELL, JOHN2, 1 2
ABSTRACT- The number of flowers open at one time on a plant can alter pollinator behavior, which may in turn alter plant reproductive success and mating system. To investigate this, we experimentally manipulated the daily floral display of monkeyflower (Mimulus ringens) plants in four replicated artificial populations during summer 2000. During 30 hours of observation, we recorded over 250 pollinator foraging bouts and 4000 floral probes. Bombus fervidus was the most common visitor (68% of foraging bouts), while B. impatiens and B. griseocollis were the only other common visitors. Bee activity began between 5:30 and 6:30 AM most mornings, peaked around 9:00 AM, and declined dramatically by 11:00 when nectar and pollen supplies were exhausted and stigmas were unreceptive. Flowers typically received 0.6 probes/flower/hour, and visitation per flower did not vary significantly with floral display treatment. The bee species did not differ in the proportion of flowers they probed during their tenure on a plant. However, early in the morning all bee species tended to probe fewer flowers per plant than they did in the late morning when nectar and pollen were scarce. Bombus fervidus had longer foraging bouts (visited more flowers before leaving the array) than did the other species, and this pattern became stronger later in the morning. These changes in pollinator behavior have important implications for the mating biology of this plant.
KEY WORDS: POLLINATOR, MATING SYSTEM, SCROPHULARIACEAE, POLLEN