Impact of Ludwigia hexapetala on native plants
Ludwigia hexapetala (Onagraceae) is native to South America and is an invasive alien aquatic plant species in the EPPO region. It has been grown as an aquatic ornamental species in the EPPO region and has escaped or been dumped as garden waste, subsequently becoming an invasive species in France, Italy and Spain. L. hexapetala can alter freshwater habitats by forming dense mats both in the water and along banks. Additionally, it can outcompete native plant species and have negative impacts on ecosystem services. One native species that can be threatened by L. hexapetala is Utricularia australis (Lentibulariaceae), a carnivorous aquatic species that has conservation status in Italy. A 21-day indoor experiment was performed in which U. australis was grown on its own (control tests) and together with L. hexapetala. Water chemical parameters were analysed and the growth and morphological traits of U. australis and L. hexapetala were measured weekly. Where the two species were grown together, oxygen concentration and pH were lower and conductivity higher than in control tests. The growth of U. australis was significantly reduced (both shoot length, internode number, and fresh weight) when grown with L. hexapetala compared to control plants. Overall, the study showed that L. hexapetala alters water parameters and negatively affects the growth of U. australis. Management measures should be undertaken against invasive populations of L. hexapetala to promote and restore native biodiversity.
Sources
Pelella E, Questino B, Ceschin, S (2023) Impact of the alien aquatic plant Ludwigia hexapetala on the native Utricularia australis: evidence from an indoor experiment. Plants 12, 811. https://doi.org/10.3390/plants12040811