Abstract Detail

Reproductive Processes

Ison, Jennifer [1], Tuan, Elizabeth [2], Koski, Matthew [3], Whalen, Jack [2], Galloway, Laura [4].

The Role of Pollinator Preference on the Maintenance of Pollen Color Variation in American Bellflower.

Polymorphisms in petal color have been well studied, however mechanisms that contribute to variation in pollen color have received less attention. American Bellflower (Campanula americana) is a common herbaceous plant with pollen ranging from white to deep purple. Pollen color in C. americana displays a longitudinal cline where westerly populations have a prevalence of purple pollen, likely due to abiotic selection for heat stress resistance. However, factors contributing to the predominance of white and light purple pollen in eastern populations and the maintenance of polymorphic populations throughout the range remain unclear. We examined pollinator-mediated mechanisms for the prevalence of white pollen in eastern populations of C. americana. Specifically, we asked the following questions: 1) Are pollinators able to use pollen color as a visual cue in C. americana? 2) Do wild pollinators exhibit a preference in pollen color? 3) If so, does preference vary based on pollen morph frequencies? In a flight cage experiment, we demonstrated that Bombus impatiens foragers can use pollen color as a reward cue. We then established floral arrays consisting of white and purple pollen plants adjacent to two naturally occurring C. americana populations. We varied the pollen morph frequencies in the arrays and observed foraging patterns of wild bees, totaling over 1,100 individual visits. The specialist pollinator, Megachile campanulae, displayed a strong and consistent preference towards purple pollen regardless of morph frequencies. The other main pollinators, Bombus sp. and small bees (mostly Halictidae), displayed no pollen color preference. Both Megachile and small bees exhibited a bias toward male phase flowers and have been shown to deplete pollen from natural populations. Taken together these results suggest that Megachile may reduce the reproductive success of plants with purple pollen, resulting in the prevalence of white and light purple pollen in eastern populations of C. americana. Our research demonstrates that pollinator-mediated selection can play a role in the maintenance of pollen color variation in natural populations.

1 - The College Of Wooster, Biology Department, 1189 Beall Ave., Wooster, OH, 44691, United States
2 - The College of Wooster, The College of Wooster (Biology Dept), 1189 Beall Ave, Wooster, OH, 44691, United States
3 - University Of Virginia, Biology, 057 Gilmer Hall , Charlottesville, VA, 22902, United States
4 - University Of Virginia, Biology Department, P.O. Box 400328, Charlottesville, VA, 22904, United States

Keywords:
Plant-Insect interaction
Floral traits
pollination
Campanula americana
Megachile
Bombus
polymorphism
pollen
Pollinator preference
Geographic cline.

Presentation Type: Oral Paper
Session: 29, Reproductive Processes II
Location: 111/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 1:30 PM
Number: 29001
Abstract ID:470
Candidate for Awards:None