Hidden Stories of the Ground Layer: Potential Mechanisms Driving Community Changes in Invertebrates due to Microstegium vimineum

Invasive plants, when successful, outcompete natives and can result in major reductions in local botanical biodiversity. In consequence, the altered plant species composition following invasion can induce change in higher trophic levels. In the southeastern United States, a widespread case of an invasive plant is Microstegium vimineum or Japanese Stiltgrass. Since invertebrate community effects of M. vimineum have varied across studies, this research investigates potential mechanisms leading to M. vimineum effects on higher trophic levels. Invertebrates were caught using pitfall traps in 4 types of treatment plot: control plots (naturally uninvaded by the grass), MV plots (fully covered by the grass), MVR plots (previously covered by the grass but M. vimineum then removed), and shade plots (uninvaded by the grass and covered by two layers of black mesh material). Taxa, feeding groups, and size categories (length in mm) were each analyzed for significantly different responses (measured by quantity) to the different treatment types. Five of these groups showed significant, with p < 0.5, differences in quantity between treatment types: Cosmetidae, Formicidae, Spirobolidae, omnivores, and predators. Since the groups varied in how the treatments affected them, the results of this study emphasize the importance of understanding that the same stimuli can be beneficial, harmful, or neutral to different groups. Therefore, the effects of invasive plants on the overall invertebrate community are dependent upon the taxa that comprise the invertebrate community.