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Scheidel, Anna [1], Borowicz, Victoria [2].

Hemiparasites do (and don’t) affect biodiversity in prairie restorations.

Photosynthetically competent root parasites (“hemiparasites”) can significantly affect the composition of a grassland. The magnitude and direction of their effects on community composition and mechanisms producing these effects have not been well documented, especially for temperate perennial root hemiparasites. When dominant species in a community are more susceptible or less tolerant of parasitism, hemiparasites can increase diversity, and this potential as keystone species makes hemiparasites of particular interest to managers seeking to increase or maintain grassland community biodiversity. Hemiparasites can also promote diversity through the role of ecosystem engineer if they redistribute limiting nutrients that are concentrated in their litter to less competitive species that are more resistant or tolerant of parasitism. In 2019 we conducted vegetation surveys and measured nitrate and phosphate in soil on two sites in which hemiparasites were well-represented in the community to determine whether the abundance of hemiparasites was consistent with keystone effects and ecosystem engineering.
Castilleja sessiliflora, a short-lived perennial, was studied on a 4-yr-old restoration located on sandy hills. Pedicularis canadensis, a longer-lived rhizomatous perennial of particular interest for prairie restoration, was studied on a mesic restoration that was >20 yrs old. Pedicularis canadensis was added in 2006-2008. Both sites are in Nachusa Grasslands, Lee Co., Illinois. Compared to plots without hemiparasites, plots with C. sessiliflora had higher species richness due to more forbs. Higher floristic quality in the presence of C. sessiliflora indicates these forbs were more characteristic of undisturbed prairie. Soil phosphate levels were higher in plots with C. sessiliflora, suggesting that ecosystem engineering could be a mechanism for these effects, but a manipulative study is needed to confirm causation. Survey of plots in the P. canadensis prairie indicated no associations between any metrics and the hemiparasite. Compared to the site with C. sessiliflora, phosphate levels were much lower, but P. canadensis was not associated with significant differences in any nutrients. While P. canadensis had no effect in our study some other research on this hemiparasite has shown increased diversity but also reduced productivity. We know of no similar study of C. sessiliflora for comparison. Keystone effects of hemiparasites can be strong, but the contribution through ecosystem engineering deserves greater attention. A better understanding of how biotic and abiotic factors shape interactions between hemiparasites and grassland communities will benefit the conservation of this threatened habitat.

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1 - Illinois State University, School of Biological Sciences, 4120/School of Biological Sciences, Normal, IL, 61790-4120, US
2 - Illinois State University, School Of Biological Sciences, Campus Box 4120, Normal, IL, 61790, United States

keystone species
ecosystem engineer

Presentation Type: Oral Paper
Session: ECO6, Ecology: Restoration and Conservation
Location: /
Date: Thursday, July 22nd, 2021
Time: 3:00 PM(EDT)
Number: ECO6001
Abstract ID:892
Candidate for Awards:None

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