The indirect impacts of white-tailed deer overabundance (Odocoileus virginianus) on forest ecosystems are not well understood, particularly their leaf-litter invertebrate communities. Long-term studies with deer exclosures (>10 years) conducted in forests of the Miami University Natural Areas suggest a significant relationship between the presence of white-tailed deer and the abundance and diversity of ant populations. In the temperate deciduous ecosystems, the common ant species are seed dispersers, particularly for native wildflower species. Since deer have negative impacts on ant communities, we hypothesized that seed dispersal would be greater in the absence of deer (exclosures) compared to those with deer activity present (controls). To test this hypothesis, we designed an experiment to monitor the rate of seed removal as performed both in the presence and absence of deer. We set up a total of five sites with a pair of transects, one in deer exclosures and one in deer access plots, consisting of three petri dishes placed 5 m apart along transects.. Each petri dish was fitted with a grid in which a total of twelve seeds were placed, consisting of four different plant species: Wild Ginger (Asarum canadense), Dutchman Breeches (Dicentra cucullaria), Trillium spp., and common Hepatica (Hepatica nobilis). The number and type of seeds removed were recorded daily for a total of two weeks. Dutchman’s Breeches experienced the highest average removal rate of the four species, with Trillium experiencing the second highest. There was a statistically significant difference between the rate of seed removal in the control plot versus the exclosure plot (chi-square=8.83, p=0.0030). The exclosure plot showed a higher rate of seed removal, indicating that the presence of deer has a negative effect on seed dispersal carried out by ants. Seed dispersal is an essential ecological function and the results of this study suggest that high deer populations may be having a negative effect on the ecosystems they inhabit.
Author: Michaela Dray
Faculty Advisor: Thomas O. Crist, Biology
Graduate Student Advisor: Gwendolyn Lloyd, Biology
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