Assistant Professor University of Tennessee Knoxville, Tennessee
Background/Question/Methods
Bees prefer visiting inflorescences with high quality nutritional rewards, including pollen and nectar. While foraging, bees are sensitive to plant volatile compounds, yet it remains unclear what drives a pollinator to land on a specific plant or individual inflorescence. The combination of a bee’s preference for higher quality resources and sensitivity to plant volatiles introduces the possibility that bees may associate certain compounds with resource quality. To establish a potential coupling between nutritional quality and volatile emissions, paired experimental field plots with three focal plant species (Helianthus occidentalis, Senna marilandica and Pycnanthemum muticum) were treated with fertilizer or water over two field seasons. The fertilizer application was hypothesized to make plants more attractive to visiting bees relative to unfertilized plants. We quantitated protein levels in p<span style="color: black; mso-color-alt: windowtext; border: none windowtext 1.0pt; mso-border-alt: none windowtext 0in; padding: 0in; background: white;">ollen collected during the bloom of each species. Volatiles were collected from inflorescences using air traps and analyzed with chromatography-mass spectrometry (GC-MS). Visitation rates were tabulated from pollinator visits and inflorescence counts.
Results/Conclusions
Preliminary results showed that protein and volatile emissions varied by plant species. Fertilizer-treated S. marilandica and H. occidentalis had significantly higher pollen protein levels than the P. muticum. Volatile emissions were significantly higher in fertilizer-treated H. occidentalis and certain compounds were emitted at higher concentrations than in unfertilized plots. Pollinator visitation rates varied by plant species but there were no differences between fertilized and unfertilized plots. Our results help inform the ways in which pollinators make foraging decisions in a floral community.
