Terrestrial invasive plant species have many negative impacts on terrestrial communities, including allelopathic effects mediated by plant chemicals. However, little is known about effects on of these species as inputs into aquatic systems and also how any effects compare to those of native species. We studied a suite of ten invasive and native species, some with known allelopathic effects. Microstegium vimineum (Japanese stiltgrass), Lonicera maackii (Amur honeysuckle), Pyrus calleryana (Callery pear), Rhamnus fragula (glossy buckthorn) and Ligustrum sinense (Chinese privet) are invasive species that have the potential to enter aquatic systems such as wetlands, streams and treeholes. Native species studied include Platanus occidentalis (sycamore), Juglans nigra (walnut), Quercus rubra (red oak), Acer rubrum (red maple) and Liriodendron tulipifera (tuliptree). For each species, a leaf extract was created by soaking leaves in distilled water for two weeks. Leaf extracts were then diluted to three additional concentrations. Adult Daphnia magna were then added to each leaf extract at four concentrations replicated 4 times. Survival of Daphnia was recorded daily for ten days.
Results/Conclusions
There was a significant overall effect of concentration, with the highest concentration of extracts having significantly lower survival than that of the lowest concentration of extracts. The species that had the largest negative effect on survival were Pyrus calleryana and Rhamnus fragula. The two species that had the least negative effect were Juglans nigra and Acer rubrum. The remaining 6 species had effects that were intermediate. There was not an overall negative effect of invasive species compared to native species, but it is important to note that the two species with the highest effects were invasive and the two species with the lowest effects were native. These results suggest the potential for invasive species to negatively impact aquatic systems compared to native species, but the strength of the effect can vary by individual species, with some native species tending to have more negative impacts that some invasive species.