One of the benefits of our second campus is that we get to practice land management and stewardship in new ways. For the first time, we are able to independently make decisions about how we engage with the land, which includes our relationships with third-party researchers.

Laura Russo is an Ecology & Evolutionary Biology professor at the University of Tennessee. When she reached out to partner with us for original research on native plant preferences of native pollinators, we jumped at the opportunity to collaborate on research that could inform the species we choose to plant to enhance the biodiversity of the land. Laura provided a summary of the project, “Native perennial plantings for native pollinators in eastern Tennessee,” below; this research was conducted by Laura Russo, Karl McKim, and Sydney Baldwin, with acknowledgments to Erin Canter, Elizabeth Davis, Paul Super, and Sam Droege.

We established 8 research plots of 18 perennial species native to Tennessee in the spring of 2022 at the Great Smoky Mountains Institute at Tremont. The plots all contained six plant species and four individuals of each plant species in rows. Two of the plots represented the family Asteraceae, two represented Lamiaceae, and 2 were Fabaceae, with the final two plots comprising two species from each of the three aforementioned plant families. Across the summer of 2022, we visited the plots weekly, weeding and watering the plants to maintain the plots, and collecting data on the flower-visiting insects and the number of flowers each plant species produced each week. 

Figure 1 – Photographs of the four plot types used in the experiment.

The GSMIT plots were part of a larger experiment across eastern Tennessee, which we called the “Feed a Bee” experiment because the funding for the initial plots came from Bayer’s Feed A Bee program ($5,000 awarded to L. Russo in 2019). The plots were established across a range of different land uses, including agricultural and urban, and we added the Tremont sites in 2022 to reflect a more natural landscape. The publications on the previous aspects of the experiment include: Khalil et al 2023, McKim et al 2023, Murray et al 2024, and Eldridge et al, in review (see works cited below).

We collected 52 species of flower-visiting insects during the summer of 2022. Most of the insects were bees, with the single most abundant species being the European honeybee (Apis mellifera). However, butterflies, including the Pearl Crescent (Phyciodes tharos) and Silver spotted skipper (Epargyreus clarus), were both relatively abundant. 

Figure 2 – A summary of the experimental design of the whole project.

At Tremont, the most popular plant species across all insects was the dwarf indigo (Amorpha herbacea). The dwarf indigo also had the highest species richness of flower visitors at the Tremont site. Seven species of insects were found only at the Tremont site: Cycloneda sanguina, Epicauta funebris, Trichopoda lanipes, Hoplitis pilosifrons, Megachile albitarsis, Megachile inimical, and Phyciodes tharos.

Figure 3 – The size of the floral display of the plant species in our study. Red is Asteraceae, blue is Lamiaceae and yellow is Fabaceae. Click to enlarge.

Figure 4 – The average abundance of visitors to the three different plant families. Click to enlarge.

Figure 5 – Box and whisker plots of the abundance and species richness of pollinators to the different plant species at the Tremont plots in 2022. Click to enlarge.

We can contrast the results from GSMIT with the rest of our study sites, where we spent 271 hours over  4 years collecting ~17,051 (198 species) of flower-visiting insects, 74% of which were native bee species. Experiment-wide, the plant species with the highest abundance of visitors was the rock aster (Eurybia  saxicastelli). Among the different plant families, the Asteraceae and Lamiaceae supported an overall higher abundance of visitors than Fabaceae, but Fabaceae supported different pollinator species than the other two families. 

Based on the results of our study, we generated recommendations for pollinator-friendly plantings in eastern Tennessee (McKim et al 2023). From a basic research perspective, we illustrated that the accessibility of a flower (e.g. whether it has a keel petal or is buzz-pollinated) interacts with its nutritional quality to affect flower visitor preferences (Murray et al 2024). We also demonstrated that the nutritional quality of the flowers was not indicated by the scent profile of the flowers (Murray et al  2024). From a landscape perspective, we demonstrated that the identity of the plant species has a much bigger effect than the land-use surrounding the plots, but that certain insect visitors were affected by broader land-use patterns (Khalil et al 2023). We also showed that agricultural land-use around the research sites did not lead to significant homogenization in the pollinator community (Eldridge et al, in review). We presented the results of this work at four scientific meetings, and several outreach events including the UTK Arboretum at Oak Ridge and an episode on the podcast Backyard Ecology, linked below.

Future Work 

We are in the process of preparing an additional publication that includes the more natural landscape of the Tremont study site into the overall picture of the Feed a Bee study. We have two undergraduate publications in progress: one involving the effect of land use on bee body size, and another on the effect of plant height on flower visitation. We also want to explore how different mixtures of plant species affect pollinator preference, and whether co-flowering communities change our perspective of pollinator preference. Overall, we hope to publish several more papers with this dataset and learn even more from this valuable community of insects. 

Supplemental Figures – Ordination analysis of the overlap in the pollinator community across the different landscapes (T =  Tremont, O = Organic Farm, A = UTK Arboretum, P = Cumberland Plateau, and G = UTK Gardens) and  different plot types (F = Fabaceae, A = Asteraceae, L = Lamiaceae, M = Mixed). Click to enlarge.

Laura shared her research on Backyard Ecology Podcast. Listen in: