Hidden fronts of invasion: Fine-scale boundaries reshape native plant communities

Invasion-driven ecological transitions remain underrepresented in fine-scale analyses, despite their central role in reshaping native vegetation. This study investigated how the invasive species Asclepias syriaca alters community structure at the boundaries of invaded and non-invaded sandy grasslands in Central Hungary. Using high-resolution transect sampling and quantitative boundary detection methods (Moving split window analysis with Squared Euclidean distance and Differential Renkonen index), compositional discontinuities were assessed across six transects representing spatial replicates of invasion front zones within a shared invasion context. The results reveal that significant vegetation boundaries – termed “novel ecotones” – frequently precede or lag behind the visible shoot front of A. syriaca , indicating complex, non-linear invasion dynamics. These boundaries vary in sharpness, width, and spatial offset, suggesting that A. syriaca impacts community structure beyond its current spatial distribution. Contrary to expectations, species richness remained relatively stable, with shifts primarily affecting species dominance patterns rather than outright loss. The identification of ecotonal dissimilarity maxima demonstrates that spatial boundary metrics can help reveal invasion-related spatial patterns and can inform conservation and management strategies, particularly in identifying ecologically sensitive transitional zones. The approach appears more suitable for detailed ecological assessment and management planning than for rapid early detection. In particular, it may help identify transition zones where early intervention could be more effective. This study contributes to the integration of invasion ecology and boundary theory, emphasizing the spatial dimension of biotic restructuring by invasive species.