Boxplots comparing richness and number of occurrences of the total recorded target Invasive Alien Plant (IAPs) species (A), of cultivated individuals/populations of target IAPs (B), and of spontaneous individuals/populations of target IAPs (C) across the urbanization gradient (HH: high cover (>50%) and high patch number (≥20) of artificial surfaces; HM: high cover (>50%) and medium patch number (5 < x < 20) of artificial surfaces; MM: medium-low cover (<50%) with medium patch number (5 < x < 20) of artificial surfaces; ML: medium-low cover (<50%) with low patch number (≤5) of artificial surfaces). Letters indicate significant differences according to the Mann-Whitney pairwise posthoc tests.