Floral nectar is a fundamental resource important for mediating interactions between plants and pollinators. As the primary energy source for most pollinating animals, nectar not only fuels their flight, but also can be an important determinant of pollinator reproduction. Considering its nutritional value, it should be of no surprise that microorganisms such as yeasts often colonize nectar. Yeasts may exploit nectar at the potential expense of plants and pollinators. For example, yeast metabolic activity has the potential to modify the taste and nutritional value of nectar, which may affect pollinator attraction, behavior, and subsequent plant reproduction. Given that yeasts may affect the nutritional value of nectar, they may also have effects on the performance and reproduction of pollinators. This research project will experimentally test the degree to which yeasts in floral nectar affect bumble bee pollinator behavior and reproduction, and also examine the mechanisms involved utilizing laboratory experiments. Results from this research will highlight a previously unstudied factor in plant-pollinator interactions, yeast, whose growth in nectar may mediate the mutual benefits received by plants and pollinators from one another.
Bumble bee pollination is a critical ecosystem service that facilitates both native plant reproduction and agricultural crop yield, as approximately 90% of flowering plants rely on insects or other animals for pollination. This research project will identify interactions and mechanisms that may limit bumble bee development and reproduction, insight that may be important for conservation and commercial enterprises seeking to preserve or develop species for pollination services. Moreover, by conducting this research with a commercially important pollinator for agricultural services, our results may have application to mechanisms that affect its success. Understanding mechanisms through which microbial organisms affect plant-animal systems will fill a void in our knowledge of the ecology of microbial organisms and the role they play in ecological communities.
Pollinators play a critical role in ensuring the successful reproduction of both wild and agricultural plants. Reward for this service often comes in the form of nectar or pollen that is provisioned by many plants amongst their flowers. Pollinator foraging behavior can be influenced by the quality of such rewards, and their foraging choices can influence not only plant reproduction through the movement of pollen, but also pollinator performance through successful acquisition of high quality rewards for energy and reproduction. Our research has revealed that the quality of floral rewards can be impacted by the presence and activity of microbial organisms such as yeasts and bacteria that live in flowers. These microbes utilize chemical compounds produced by plants such as sugars and amino acids for their own benefit, potentially reducing the quality of floral rewards. Given that pollinator performance is often tied to the quality and quantity of rewards consumed, changes in reward quality as a function of microbe presence and activity may have significant consequences for pollinator reproduction. To test this, we fed laboratory colonies of the common eastern bumble bee, Bombus impatiens, nectar with live or dead nectar yeasts under high and low resource (pollen) conditions and measured their reproduction. By using live and dead yeast cells, we could test for direct effects of consuming yeast cells versus effects through changes in nectar generated by live yeast activity. We found that yeasts benefited pollinator reproduction, but only under low resource (pollen) conditions. This finding suggests that yeast cells may serve as an additional source of nutrition for pollinators, but only when resources are low. These results have important implications for pollinator health in poor resource environments. This award provided training and research opportunities to a graduate student. The graduate student has finished his dissertation and is now a post-doctoral associate. The award also provided the graduate student the opportunity to mentor three undergraduate students in research (two of whom were women). All three of these students are still working towards obtaining undergraduate degrees; one of them is a declared biology/geology major and the other two have not had to declare their majors yet.
