PARENT SESSION
Poster Session #50: Evolutionary Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
122
The effect of interspecific competition for pollinator service on pollen dispersal and gene flow in mixed arrays of Mimulus ringens and Lobelia siphilitica.
Bell, John1, Karron, Jeffrey1, Mitchell, Randy2, 1 2
ABSTRACT- Pollinator movement within a plant community is dependent on the number of plants that are flowering, the number of species that are flowering, and the floral reward for each flower visited. Thus, the fate of an individual plant's male and female reproductive success is often contingent upon other plants in its immediate neighborhood. Competition for pollinator service among plants will occur whenever there are too few pollinators to provide flowers with sufficient conspecific pollen, or when pollinators do not exhibit floral constancy and interspecific pollen movement reduces reproductive success. Natural populations of Mimulus ringens and Lobelia siphilitica have similar flower shapes and color, share pollinators, but bloom sequentially with moderate overlap. My current research explores how interspecific competition for pollinator service influences the mating system of M. ringens. Plants of M. ringens with unique marker genotypes have been placed in uniform experimental arrays in competition with L. siphilitica. Population density and spacing were kept constant, facilitating a detailed analysis of the effects of a competing species on patterns of pollinator movement and pollen-mediated gene dispersal. During a previous experiment, the large quantities of M. ringens pollen on L. siphilitica stigmas indicate that heterospecific pollen transfer occurs frequently. This heterospecific pollen transfer may lead to reduced outcrossing rates, reduced seed set (female reproductive success), and reduced siring success (male reproductive success) in M. ringens.
KEY WORDS: mating system, gene dispersal, interspecific competition, heterospecific pollen