PARENT SESSION
Oral Session # 34: Plant Ecology II: Pollination and Dispersal.
Presiding: A McEuen
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 202.

Discerning pollinators and depraved plants: Inbreeding history alters bumblebee visitation frequencies to Mimulus guttatus.

Carr, David^*,1, Roulston, T'ai¹, ¹ University of Virginia, Boyce, VA

ABSTRACT- The majority of plant mating-systems include at least 20% selfing, and restrictions in gene flow by seeds and pollen make biparental inbreeding ubiquitous. Inbreeding is typically associated with reduced offspring fitness (inbreeding depression). Previous work on the yellow monkey flower, Mimulus guttatus, had shown a 30% reduction in pollen production by offspring produced from selfing. Because pollen is an important reward for pollinators in this species, we examined visitation patterns by a bumblebee, Bombus impatiens, in a greenhouse population of 960 M. guttatus comprising equal numbers of outbred plants, plants from a single generation of selfing, and plants from two consecutive generations of selfing. Eight plants from a particular M. guttatus family and inbreeding level were grouped together, and 24 of these octets were randomly arranged on each of five benches. Each morning over a 17-day period we released B. impatiens from a captive hive and allowed them to forage freely on M. guttatus flowers for 75 minutes. Two observers starting at different benches recorded visitation by following the sequence of visits of focal bees beginning with their arrival at a bench. Observers rotated to a new bench every 15 minutes. Although bees visited similar numbers of flowers when arriving at each type of octet, bees were 21% more likely to visit outbred octets than they were octets from a single generation of selfing and were 48% more likely to visit outbred octets relative to octets from two generations of selfing.

Key words: pollinator, Bombus, inbreeding, Mimulus