OOS 37-4 - Shifts in arthropod trophic structure following plant invasion: Lessons from restored grasslands

Thursday, August 10, 2017: 9:00 AM
D136, Oregon Convention Center
Adam B. Mitchell, Entomology and Wildlife Ecology, University of Delaware, Newark, DE, Andrea R. Litt, Department of Ecology, Montana State University, Bozeman, MT and Douglas Tallamy, Entomology and Wildlife Ecology, University of Delware, Newark, DE

The introduction of aggressive, nonnative plants into landscapes may reduce local biodiversity and ecosystem services by reducing the presence and abundance of native plants, with concomitant effects for native fauna. Arthropods may be severely affected by native plant loss, as arthropods share close coevolutionary relationships with their host plants and are sensitive to environmental changes. We report two separate studies that quantified changes in the biodiversity and structure of arthropod communities following plant invasion. We conducted a field experiment in south Texas 2011-2013 to restore native arthropod communities impacted by a nonnative grass. We conducted a series of field studies throughout the Mid-Atlantic region in 2015 to compare trophic structure of arthropods in restored grasslands to arthropods in communities dominated by 1 of 8 nonnative plants. For both studies, we sampled arthropods within plots of each community using a variety of sampling techniques to capture as much of the community as possible (pitfall traps, vacuum sampling, Berlese-Tullgren funnels). When possible, we identified all arthropods to species, and assigned each unique taxa to a functional group (herbivores, detritivores, predators). We explored differences in richness and abundance of arthropods and functional groups between plant communities.


Overall, we observed a greater diversity of all functional groups in restored grasslands than nonnative grasslands for our field experiment in Texas. However, there were more herbivores (individuals/m2) in nonnative grasslands than restored grasslands, due to the abundance of a nonnative leafhopper that may use the nonnative grass as refugia in the leafhopper's introduced range. Nonnative pillbugs were the dominant detritivore in both grasslands, and became more abundant in restored grasslands over time. In our field studies throughout the Mid-Atlantic, we observed a greater diversity of all functional groups in restored communities than communities dominated by nonnative plants. For all 8 species of nonnative plants, we recorded fewer herbivores than in communities with native plants. Although the difference varied significantly among the 8 selected plant species, all nonnative plant communities had more detritivores than herbivores, and detritivores were dominated by nonnative taxa. A shift from a community driven by herbivores to one driven by detritivores, or a ‘green-to-brown’ shift in the food web, may have negative consequences on restoring ecosystem services to landscapes impacted by nonnative plants. The presence of nonnative arthropods may also mask or inhibit restoration success, requiring tools to identify and monitor these taxa during restoration projects.