Uniqueness matters: patterns of α and β-diversity highlight conservation priorities for plant communities in Italian agricultural landscapes

Agrosilvopastoral management can increase the levels of biodiversity in the landscape by increasing the diversity of ecosystems1. To assess their conservation priority based on contribution to plant diversity, in spring-summer 2023 we surveyed plant communities in 25 m2 square plots in croplands, grasslands, shrublands, forests, and wetlands in 50 circular, 1 km-radius agricultural areas across Italy. We compared the five ecosystem types in terms of plant community α-diversity, β-diversity, and species composition using analysis of variance and Indicator Species Analysis (INSPAN). The α-diversity was significantly higher in grassland ecosystems and significantly lower in wetland ecosystems. Local contribution to β-diversity (LCBD) negatively correlated with α-diversity. The highest LCBD was given by wetland plant communities, which were then the most unique in species composition, followed by cropland and grassland plant communities. However, the plant communities of all the ecosystem types contributed to β-diversity. The species contributing the most to β-diversity were wetland species like Phragmites australis, Myriophyllum spicatum, and Lemna minor and woody species like Prunus spinosa, Rubus ulmifolius, and Quercus spp. All the ecosystem types differed from one another in plant community species composition based on PERMANOVA, and they hosted distinctive species based on INSPAN. By highlighting their uniqueness in composition, we showed that wetland plant communities had the highest conservation priority. Nevertheless, we suggest that maintaining a high diversity of ecosystems is pivotal to preserve the overall plant diversity. Conservation strategies should focus on the maintenance of diversified agricultural landscapes, including anthropogenic, natural, and semi-natural ecosystems.