Planting roots: distribution pattern of invasive alien plants in urban habitats of Campobasso (Italy)

across urban environments is essential for developing effective management strategies and mitigating their impacts on urban, peri-urban, and natural habitats. This study examines the occurrence and spatial distribution of a set of IAPs along an urbanization gradient and across EUNIS Habitats in a Mediterranean city of Southern Italy (Campobasso). The study was carried out across 14 urban grid cells (500 m × 500 m) reflecting different levels of urbanization. 26 IAP species were surveyed according to a national standardized protocol; for each record, GPS coordinates, cultivated versus spontaneous status, EUNIS Habitat type, and cover area were recorded. The influence of urbanization on IAP richness and occurrence was assessed using Mann–Whitney tests. For species with predominantly spontaneous occurrences (>80%), we analyzed their distribution across EUNIS Habitats and cover area classes. Grid cells with high cover and patch number of artificial surfaces were associated with significantly greater IAP richness and occurrence values. Slightly more than half of the total records consisted of spontaneously established individuals or populations belonging to ten species, with Senecio inaequidens, Robinia pseudoacacia, and Ailanthus altissima being the most frequent. Transport networks and other hard-surface constructed areas, followed by dry perennial anthropogenic herbaceous vegetation, emerged as the most invaded habitat types. Overall, the findings highlight the need for early detection and prevention efforts targeting “emerging” invasive species that, although currently infrequent, may possess high potential for future expansion.