Ecosystem impacts of Impatiens glandulifera
Impatiens glandulifera (Balsaminaceae: EPPO List of Invasive Alien Plants) is an invasive, annual species native to the Western Himalayas. It was originally introduced into the EPPO region as a garden ornamental and has spread throughout Europe. I. glandulifera can produce allelopathic chemicals which contain the main compound 2-methoxy-1,4-naphthoquinone (2-MNQ), which has been shown to inhibit the germination of common native European plants, and ectomycorrhizal fungi. As I. glandulifera often forms monocultures along riverbanks, there is the potential for allelopathic chemicals to be leached into waterbodies. Mesocosm experiments were conducted to test the impact of I. glandulifera on the population growth of Daphnia magna (Daphniidae) and the green alga Acutodesmus obliquus (Chlorophyceae). Six I. glandulifera potted plants were positioned over water tanks filled with water which contained a known amount of D. magna and A. obliquus at the start of the experiment. Natural rainfall acted to leach chemicals from the soil into the water tank. The experiment was replicated 12 times and a control (potted soil but no I. glandulifera) was used. The population growth of D. magna was lower in the mesocosms with I. glandulifera after a period of strong precipitation compared to the control. Separate laboratory experiments using the main allelochemical released by I. glandulifera, 2-MNQ, showed negative effects on the population growth of A. obliquus and the growth of D. magna. These results suggest that allelochemicals leached from I. glandulifera can have negative impacts on organisms at an ecosystem level.
Sources
Diller JGP, Drescher S, Hofmann M, Rabus M, Feldhaar H, Laforsch C (2022) The Beauty is a beast: Does leachate from the invasive terrestrial plant Impatiens glandulifera affect aquatic food webs? Ecology and Evolution 12, https://doi.org/10.1002/ece3.8781