The interplay of landscape connectivity, composition and configuration in alien plant invasions across an ecological network

Context Biological invasions are deemed to be the second most important global driver of biodiversity loss showing strong interactions with the aftermaths of land use change and landscape fragmentation. The role of landscape composition and configuration in biological invasions is widely considered while its interplay with landscape connectivity is less understood. However, ecological connectivity can be equally crucial for both native and alien species, constituting the backbone of ecological network initiatives. Objectives We aim to assess how landscape composition, configuration and connectivity (in the ecological network) influence α- and β-diversity (floristic uniqueness) of both alien and native plant species, and to determine whether these effects differ according to habitat type. Methods The study was conducted in a 298 km 2 ecological network in the lowlands of Friuli Venezia Giulia, northeastern Italy, encompassing a mosaic of agricultural, natural, and semi-natural habitats. A hierarchical sampling design was applied to 87 terrestrial habitat nodes, where plant species composition and abundance were recorded in 219 plots. Landscape composition, configuration and connectivity were quantified to examine their influence on native and alien plant α- and β-diversity across different habitat types. Results We found contrasting effects of landscape connectivity, composition and configuration for native and alien species. Peripheral, less connected sites favored native species richness (α-diversity) and contributed to maintaining native floristic uniqueness (high β-diversity). In contrast, alien species richness was mainly associated with landscape composition and configuration, particularly the proportion of natural land use and edge-related effects in wooded habitats, while plots with higher alien richness showed lower compositional uniqueness within the alien species pool. Landscape composition and configuration also influenced invasion dynamics, as nodes surrounded by a high proportion of natural land uses with simple shapes helped contain plant invasions while preserving native richness and uniqueness. These patterns were often habitat-dependent, with stronger effects observed in wooded areas, where alien α-diversity increased with fragmentation, whereas native species richness declined. Conclusions Our findings suggest that managing landscape connectivity and reducing fragmentation can enhance resistance to invasions and support native species richness. Peripheral nodes may act as native refugia, supporting high native richness and floristic uniqueness, while more accessible central nodes may function as alien hubs associated with greater alien compositional uniqueness and potential propagule exchange. Shifting from intensive to extensive land uses through green infrastructures provides a win–win strategy, promoting native species and limit alien establishment.