The overabundance of white-tailed deer (Odocoileus virginianus) and the presence of invasive plants, such as Amur honeysuckle (Lonicera maackii), have strong effects on deciduous forest ecosystems of eastern North America. Deer and Amur honeysuckle reduce abundance and diversity of plants in the forest understory and affect ecosystem processes, but few studies have examined how they alter litter-dwelling arthropods. Ants (Formicidae), in particular, play key functional roles in forest ecosystems, acting as ecosystem engineers, predators, and seed dispersers. Changes to ant abundance and community structure may have cascading effects on various ecosystem processes. We hypothesized that removal of deer and invasive honeysuckle would increase the abundance of ants and increase standing litter biomass. We analyzed ant species composition, richness, and abundance from five sites in southwestern Ohio from 2011 to 2017. Each site consisted of a 20x20 m deer exclosure paired with a control plot, each with a split-plot removal of honeysuckle. All ants were sampled using Winkler funnel litter extraction.
Results/Conclusions
Deer removal significantly increased ant abundance and richness over time compared to the control plots. By the end of the study, we saw as much as a 300% increase in ant abundance in deer removal plots, while we saw as much as a 100% increase in ant richness in deer removal plots compared to the deer access plots. Additionally, both ant abundance and richness were positively related to standing litter biomass. Deer removal significantly increased standing litter biomass relative to the control plots. We found no direct effect of honeysuckle on ant abundance, ant richness, and standing litter biomass. While ant abundance and richness changed in response to deer removal, we saw no effect of any of our treatments on ant community composition. Our results show that deer negatively affect litter dwelling ants, supporting the hypothesis that differences in abundance and diversity of litter dwelling arthropods between deer access and removal plots result from reductions in standing litter biomass. Our study is the first continuous long-term study of deer removal effects on litter dwelling organisms. The direct and indirect effects of deer on standing litter biomass and ant communities potentially have cascading effects on other litter dwelling invertebrates and ecosystem processes in forest ecosystems. Reduction of overabundant deer populations may increase the biodiversity of litter dwelling insects.