Are some communities of the coastal dune zonation more susceptible to alien plant invasion?

Coastal areas, and in particular coastal dunes, are ecosystems\udstrongly affected by the invasion of alien plants. However, few\udattempts have ever been made to quantify alien species incidence\udin different communities along the coastal zonation. This work aims\udto analyze the distribution of alien plants along the coastal zonation\udof sandy shores on the Tyrrhenian coast, addressing specifically differences\udamong plant communities in abundance of alien plants.\udMethods\udThe study was performed on recent dunes (Holocene) of the central\udwestern coast of Italy. We selected dune landscapes where invasion\udprocesses were particularly evident. Vegetation plots were randomly\udsampled and through cluster analysis, we identified six plant communities\udcorresponding to the typical zonation described for the\udTyrrhenian sandy coast of Central Italy.We evaluated and compared\udfrequency and abundance of invasion in these different communities.\udFurther, we investigated how propagule pressure (measured using\udas proxy human structures) contributed to the observed invasion\udpatterns.\udImportant Findings\udWe found a relatively low total number of aliens but also a differential\uddistribution pattern and strong abundance of some of the aliens in\udspecific sectors of the vegetation zonation. The perennial community\udof transition dunes appears most affected by invasion processes,\udrelated almost exclusively to the frequent and widespread Carpobrotus\udaff. acinaciformis. This alien species reaches high cover values,\udapparently lowering cover of native species of transition dune plant\udcommunities. Higher levels of invasion in the transition dune can be\udpartially explained because of greater propagule pressure in this\udsection of the dune profile. Our findings thus have important\udconservation and management implications since transition dune\udcommunities with Crucianella maritima are rare and protected\ud(sensu Habitat 92/43/EEC Directive) along the entire Italian coas