ETD

• alien species
• invasive alien species
• specie aliene
• specie aliene invasive

The aim of this study is to assess the impact of two invasive alien species, the perennial herb Salpichroa origanifolia (Lam.) Baill., native to South America, and the perennial succulent Yucca gloriosa L., native to the southeastern United States, on plant communities in two protected areas within the ‘Parco Naturale di Migliarino–San Rossore–Massaciuccoli’, specifically by evaluating the effects of S. origanifolia on a declining coastal oak woodland community and the impact of Y. gloriosa on backdune native plant communities. For both species, effects on the standing vegetation were investigated, while for S. origanifolia the study also focused on the soil seed bank, in order to evaluate potential long-term impacts. Vegetation was sampled as percent cover in two areas (moderately and highly invaded) for S. origanifolia, in the San Bartolomeo forest, and across three invasion levels (highly invaded, moderately invaded, and non-invaded) for Y. gloriosa, on the coastal back dune of Marina di Vecchiano, while in the case of S. origanifolia soil seed bank sampling was carried out in the same two areas using the “seedling emergence approach.” Results indicate that S. origanifolia strongly impacts coastal plant communities, causing significant reductions in native species richness, diversity, and evenness, both in standing vegetation and the seed bank. Y. gloriosa, by contrast, does not affect species richness but significantly reduces diversity and evenness, promoting the dominance of a few species. In both cases, these invasions substantially modify the structure of coastal plant communities. The findings provide novel insights into the impacts of the two invasive alien species and offer valuable baseline information for the conservation of the two protected areas. Moreover, they contribute to the development of management tools aimed at controlling invasive species and restoring ecosystems that are highly disturbed by anthropogenic activities.