Variations in chemical and physical water parameters in all sampled sites. Boxplots show the median (line across the box), upper and lower quartiles (the upper and lower parts of the box), and values outside the quartiles (the whiskers). The dots represent each sampled site and their size increases proportionally with the percentage cover of L. hexapetala; reference measurements are provided in the legend. The colour of the dots also gets darker with increasing cover of the alien species. Red asterisks show uninvaded sites where L. hexapetala cover = 0.