Community types and alien species distribution in Italian coastal dunes

The present study concentrates on recent dunes (Holocene) of the Molise region (Central Italy). Wefocus on different plant communities along the coastal zonation with the aim of quantifying theirdegree of invasibility by alien plants. Vegetation data were collected following a random stratifiedsampling design, using a CORINE land cover map (scale 1:5,000) with the land cover classes as strata.In order to identify the major community types present in the study area, 125 sampling plots wereclassified through cluster analysis and ordinated with PCoA. The percentage of the flora comprisedby alien species and the mean alien species richness for each community type was calculated using aone-way ANOVA to test for significant differences. Five community types were identified along a gradientof increasing distance from the sea. Despite the higher proportion of aliens, the beach andembryo dune communities showed mainly archaeophytes, or at least species introduced many centuriesago, which have clearly adapted to the particularly stressful conditions. On the other hand,mobile dunes showed lower proportion of aliens but included neophytes. In the Mediterranean macchiathe lowest proportion of aliens was observed. Our results suggest that in coastal dune communitiesboth human disturbance and environmental stress affect alien invasions. The interaction ofthese two factors probably plays an important role in the distribution of alien species.