Impact of the Alien Aquatic Plant Ludwigia hexapetala on the Native Utricularia australis : Evidence from an Indoor Experiment

is an alien aquatic plant considered highly invasive in Europe since it alters freshwater habitats by forming dense mats both in water and along banks, outcompeting natives. effects on the native carnivorous plant were investigated here. A 21-day indoor experiment was performed by setting up some separate tests in which was made to grow both alone (control tests) and together with (arena tests). Water chemical and physical parameters and growth and morphological traits of and were analysed weekly. Water samples were also analysed by UV-visible spectra to verify allelochemical (quercitrin) production by . In arena tests, oxygen concentration and pH were lower and conductivity higher than in control tests. grew significantly less in arena tests in both shoot length and internode number, and its fresh weight, trap number and internode length decreased more than the control. Quercitrin was found only in arena tests as an allelochemical product released by . Overall, this study demonstrated significantly alters water parameters and negatively affects the growth of , showing aggressive and competitive behaviour against this native species. Such evidence suggest that the widespread of can represent a serious threat to the conservation of native plant diversity occurring in the freshwater habitats it invades.