On the basis of the classification, it was not possible to outline a clear species vs. site cluster structure. Instead it was found an evident trend of site-by-site species clustering, which was probably affected by the ecological factors characterizing every single sample site. This is the case, e.g., of the sites belonging to the A group, where the fact of belonging to the same geographical district may have influenced species distribution, while in the group C the natural and man-made disturbance is likely to be more critical than sharing the same geographical district.