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Graduation Term
Fall 2025
Degree Name
Master of Science (MS)
Department
School of Biological Sciences
Committee Chair
Victoria A. Borowicz
Committee Co-Chair
William L. Perry
Committee Member
Steven A. Juliano
Abstract
Hemiparasitic plants steal resources from hosts and through multiple pathways can alter prairie diversity and resistance to invasion, but the relative importance of theft vs. nutrient and microbial modification is unknown. This project examined how the native hemiparasite Pedicularis canadensis affects its local community, and whether P. canadensis impedes expansion of the invasive legume Lespedeza cuneata. In 2024, I recorded percent cover and species richness in 1-m2 plots for which 2019 community composition was known, organic nitrogen concentration, and microbial biomass in each plot. These 2019 and 2024 data were incorporated in piecewise structural equation modeling to evaluate hypotheses for effects of P. canadensis and L. cuneata on the community. A significant negative effect of P. canadensis on forb richness and cover, legume richness indirectly (but positive effect directly), and graminoid richness indicates the hemiparasite affects diversity of the site by altering competitive relationships but does not support the hypothesis that the hemiparasite is a keystone species. The hemiparasite significantly decreased soil organic nitrogen, which indirectly increased non-Lespedeza legume cover, supporting the hypothesis that P. canadensis behaves as a weak ecosystem engineer. Changes to species richness or evenness by P. canadensis had no significant effect on L. cuneata, failing to support the hypothesis that species-rich prairie communities are more invasion resistant. Native Lespedeza capitata had significant negative effect on L. cuneata, consistent with the hypothesis that functionally similar species can inhibit invasion. Knowing how hemiparasites like P. canadensis impact local biodiversity and invasion resistance can inform prairie management and restoration.
Access Type
Thesis-ISU Access Only
Recommended Citation
McGinnis, Cassie Nicole, "Prairie Vampires: Pathways by which Hemiparasitic Pedicularis canadensis Influences Community Dynamics in the Presence of Invasive Lespedeza cuneata" (2025). Theses and Dissertations. 2236.
https://ir.library.illinoisstate.edu/etd/2236