Mentor: Professor Neil Williams
In most flowering plant communities, individual species are visited by a diversity of pollinators, primarily bees. Surprisingly little is known about the factors that determine to which plant species the pollinators visit. Although we tend to view bees as pollinators, they visit flowers to collect food-- pollen and nectar-- that they provide their offspring. Many factors ultimately influence the number of offspring a bee produces, but in a simple sense more resources of higher quality translate into a larger brood. As a result we expect bees to visit plants with higher quality of resources. Scaling up to the whole community, if we determine the resource qualities among plants species, we can gain insight into a key mechanism underlying the visitation patterns of pollinators.
The quality of a flower species for a foraging bee is determined by (1) quantity of pollen and nectar a plant offers, (2) the abundance of that plant and (3) the ability of the bee to access pollen and nectar rewards. The match between flower and bee morphologies permit or prevent access. I will explore resource distributions and floral morphology within a flowering plant community in the Chihuahuan Desert from July-August 2007. To assess the reward quality, I will sample the pollen and nectar available per flower, the number of flowers on a plant, and the duration in which the flower is open for flowering species on a 1 ha plot. Pollen and nectar samples will be quantified upon return to the lab. These data will be combined to calculate the maximum-potential-resources available from each plant species. This represents a rough approximation of resource quality among flowers. I also will take digital photographs and use a computer program to measure flower morphology for these same flower species. These morphological data can be matched with data from different bee species to translate maximum- potential-resources into the amount available to different bee species.
The results for this research can be used to make predictions of visitation patterns within pollinator-plant communities. We can then compare our predictions to observed patterns of floral visitation by insects from the same study plot. Insect visitors vary dramatically in their quality as pollinators. Thus the identity of visitors can strongly affect plant reproduction and fitness. This study, which is part of an ongoing research program, will identify mechanisms underlying differences in pollination and plant reproduction within the context of a whole community-- something rarely attempted.
Morphological data on bees will be made by our lab and other collaborators during the fall and winter season.