Le piante aliene nel Mediterraneo: comparazione tra Sardegna, Corsica e isole circumsarde.

This research project was mainly aimed at updating and comparing the exotic vascular flora of Sardinia with that of other territories belonging to the same biogeographical region and at the analysis of the most vulnerable habitats at risk of biological invasion. The first part of the work has been focused on the comparison of the exotic flora of Sardinia with that of another insular system, Corsica, in order to acquire the information necessary to define new strategies, guidelines and priorities useful to mitigate the effects of biological invasions. First we proceeded with the updating of the checklist of Sardinia and with the implementation of a new checklist for Corsica. The checklist of the exotic vascular flora of Sardinia is composed of 598 taxonomic units (18% of the total flora), of which 344 are neophytes, 164 archeophytes and 90 dubious; 6 (our signal) are new reports. Furthermore, 168 are naturalized, 276 casual and 64 invasive. The checklist of Corsica is composed of 553 entities (17% of the total flora), of which 339 are neophytes, 127 archeophytes, 87 dubious and 27 are new reports. Moreover, 117 are naturalized, 250 casual and 99 invasive. The comparison of the two floras showed no significant differences, confirming the similarities among insular territories from the same biogeographical region; 234 exotic entities are in common between the two territories (46% of the alien flora of Sardinia and 50% of Corsica). In the second part of the thesis, a first census of the taxa present in the various little islands through the analysis of the bibliography was made. Then, a checklist with 153 taxa divided into 57 families was developed. Statistical analysis were carried out (hierarchical cluster, PCA and Bayesian analysis) to evaluate the homogeneity of the exotic vascular flora, through a matrix presence/absence, for each reported island. Moreover, other analysis (hierarchical cluster, PCA, correlation analysis and linear regression) were carried out in order to verify which values, associated with surface characteristics of the islands, insulation, type and use of soil, climatic indices and human disturbance, can positively or negatively affect the presence of exotic taxa or even of the total flora in the studied areas. The third part of the thesis focused on the most vulnerable habitats to biological invasions, those of wetlands. In particular, a study focused on the area of the Regional Natural Park Molentargius - Saline. Floristic and chorological analysis of the exotic taxa, corresponding to 107 of which 10 are of dubious exoticism, 21 are cultivated not naturalized and 21 of new signaling, have been integrated with maps of the more invasive and potentially invasive entities for the area. Maps were carried out in GIS environment, after the implementation of a geodatabase, based on regional technical map of the Autonomous Region of Sardinia (scale 1:10.000) and orthophotos of Sardinia. From the obtained results, it was possible to gain some knowledge on the behavior of exotic taxa in geographic areas with similarities from an environmental perspective and consequently, have a complete overview of the main invasive entities that threaten native habitats and species. Moreover, the acquired data may enable the development of new strategies, guidelines and priorities for action aiming to mitigate the effects of plant invasions in the studied territories, as well as in other areas with similar climatic conditions. Finally, it is important to highlight that the creation of a common monitoring network among the different areas of study could be an effective way to promote the exchange of information, cooperation and coordination (still very weak), involving all stakeholders working in the sector.