Experimentally quantifying impact of herbivory on duckweed communities in natural pond ecosystems.

Plant herbivory structures communities, impacts energy and nutrient flow in ecosystems, and drives speciation. Yet, our knowledge of plant-herbivore interactions remains limited in freshwater ecosystems compared to terrestrial ones. We still lack robust experimental data on the impact of herbivores in nature on whole families of important macrophytes such as the globally distributed duckweed family (Lemnaceae). We conducted a replicated manipulative field experiment, using exclosures, across multiple bodies of water quantifying both ambient herbivory as well as herbivory caused by the addition of two different weevil and aphid herbivores. We found that invertebrate herbivores can strongly impact duckweed multi-generational population growth (e.g., reducing daily relative growth rate by up to 82% compared to controls) and differentially impact duckweed species composition. These impacts, however, vary greatly across sites and with the identity of the herbivores. Our results suggest that insect herbivores can severely slow the growth of the of the worlds fastest growing plant family. It also provides crucial information as duckweed continue to be developed for various applied purposes such a biofuel production and bioremediation.