Invasive plants and natural habitats: The role of alien species in the urban vegetation

A survey of the alien plants' communities of the metropolitan area of Catania (Sicily, Italy) has been carried out. The area covers the central city (Catania) and a number of smaller centers (villages) connected by territorial contiguity of close integration with regard to economic activity, environmental, vital services for social and cultural relations. The component of alien species was compared to that of native ones, considering the historical and spatial aspects, and the role and presence of the non-native plants in natural habitats. Furthermore, three cases of the new recordings of exotic species have been reported.