CSR strategy shifts under biotic resistance and grazing drive invasion success of <em>Solanum rostratum</em> in northern China

Biotic resistance and environmental filter are the primary ecological barriers to successful invasions. Although the role of functional strategies in overcoming these barriers has been extensively investigated, whether and how the plasticity of functional strategies facilitates successful invasions remains poorly understood. In this study, we explored the invasion mechanisms of a widespread invasive plant, Solanum rostratum, across a 3,000 km spatial extent in northern China using Grime’s competitor, stress tolerator, and ruderal (CSR) framework. Our results showed that S. rostratum consistently invested more in C-strategy compared to native species, but it exhibited plastic shifts between S- and R-strategies. These strategic shifts were primarily influenced by the CSR strategy and the taxonomic and functional diversity of native communities, which selected for greater strategic divergence between S. rostratum and native species. Grazing further modulated these shifts by reducing native diversity. By increasing its strategic divergence from native competitors, S. rostratum may persist in species-diverse native communities and dominate in frequently disturbed and species-limited communities. Synthesis: Our findings reveal a dynamic strategy-environment matching process across space, underscoring the significance of functional plasticity in overcoming varying ecological barriers during large-scale invasions.