|Sweet, Heather - OR STATE UNIVERSITY|
Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2004
Publication Date: July 1, 2004
Citation: DeJoode, D., Brunet, J., Sweet, H. 2004. Natural selection on floral characters by different pollinators in the blue columbine: selection through female fitness [abstract]. Ecological Society of America Abstracts. Paper No. 90-2. Technical Abstract: The preference of pollinators for given floral characteristics can modify floral designs. Hawkmoths and bumblebees are the two major pollinators of the blue columbine, Aquilegia coerulea. Hawkmoths mostly visit flowers at dusk and collect nectar. Bumblebees visit flowers during the day and collect only pollen because their tongues are too short to reach the nectar at the bottom of each spur. We set up three experimental treatments to examine how different pollinators influenced selection on floral characteristics. In one treatment, plants were caged early morning and removed before dusk allowing mainly hawkmoths visits. In a second treatment, we reversed the timing of caging to allow bumblebees but not hawkmoths visits. Plants in the control treatment were not caged. For each plant in each of the three treatments we measured spur length, flower color, sepal size, and flower production (the total number of flowers per plant). All mature fruits were collected on each experimental plant and seeds per fruit counted. To estimate the strength of selection acting on floral traits within each pollinator treatment, standardized selection gradients were calculated by regressing relative total fitness on the four floral traits. Standardized selection gradients for the different floral traits were then compared among pollinator treatments. Because only hawkmoths collect nectar, we expected hawkmoths but not bumblebees to influence spur length evolution. Both pollinators were predicted to similarly influence flower production and sepal length. Bumblebees were expected to select for blue flowers; hawkmoths for white flowers. Our results confirmed some but not all of our predictions.