Urbanization Reshapes Ecological Strategies and Evolutionary Trajectories of Remnant Vegetation: Evidence from Leaf Traits and Phylogenetic Signals

Leaf functional traits are key indicators for studying urban habitat and vegetation adaptation. This study examined how remnant vegetation in Guangzhou adapts to the combined effects of environmental filtering and phylogenetic constraints across low, medium, and high levels of urbanization. Six key traits — leaf area (LA), specific leaf area (SLA), leaf dry weight (LDW), leaf total nitrogen (LTN), leaf total phosphorus (LTP), and the N:P ratio-were measured in 19 dominant species across 16 representative sites. Analyses included One-way ANOVA, Principal Component Analysis (PCA), Phylogenetic signal analysis and Phylogenetic Independent Contrast (PIC). Results showed that with increasing urbanization, LA and SLA declined, LDW and LTP increased significantly, and LTN and N:P showed non-linear patterns. Trait correlations aligned with the leaf economics spectrum (e.g., positive LA-LDW, negative LTP-N:P). However, PIC correction revealed a significant positive SLA-LTN correlation, indicating that phylogeny partially masked adaptive trait coupling. Phylogenetic signal analysis showed significant conservatism only for SLA under high urbanization (K=1.399, P=0.049). K values for other traits decreased or showed U-shaped trends with urbanization, indicating environmental filtering and competition weakened evolutionary history’s influence in medium urbanization, while extreme filtering in high urbanization reinforced phylogenetic conservatism for key traits. PCA indicated a shift from structural dominance (LA, LDW) in low urbanization to nutrient regulation (LTP, N:P) in high urbanization. Urbanization drives a shift from ”fast resource acquisition” to ”conservative resource use” strategies in remnant vegetation, involving trait synergy decoupling and dynamic phylogenetic signal changes, providing a theoretical basis for optimizing urban green space and enhancing ecosystem services.