Invasion without a shift: functional strategy structure of native and alien species of spontaneous flora in the historical dendrological park

Dendrological parks are long-term human-modified ecosystems where native and alien plants coexist under heterogeneous environmental conditions shaped by historical management and repeated introductions. We analysed the spontaneous flora of Trostianets State Dendrological Park (Chernihiv Region, Ukraine) using field surveys conducted in 2023 and 2024 and published records. A total of 423 vascular plant taxa representing 73 families were recorded, including 299 native (70.7%) and 124 alien taxa (29.3%). Functional strategies were assessed using the CSR (Competitive–Stress-tolerant–Ruderal) framework. CSR data were available for 407 taxa, including 291 native and 116 alien taxa. Native and alien taxa substantially overlapped in CSR space, and species origin explained only 0.47% of variation in CSR composition (R² = 0.0047, F = 1.89, P = 0.153). A complementary analysis of leaf functional traits also showed substantial overlap between native and alien taxa. In contrast, growth form explained 11.6% of variation in CSR composition, with woody taxa showing higher stress-tolerance and lower ruderality than herbaceous taxa. The origin × growth-form interaction was not significant (R² = 0.003, F = 1.37, P = 0.247). The introduction pathway showed an apparent association with CSR composition among alien taxa, but this pattern was strongly associated with growth form: ergasiophygophytes were predominantly woody, whereas xenophytes were predominantly herbaceous. These results indicate that alien establishment in the park has not been accompanied by a distinct shift in overall functional strategy structure. Instead, CSR variation was more strongly associated with growth form than species origin, while the introduction pathway provided a secondary source of functional differentiation within the alien flora.