Latitudinal Adaptive Strategies of Tetracentron sinense: Insights from Functional Traits and Phylogenetic Conservatism

Anthropogenic disturbances and climate warming threaten the rare paleoendemic species Tetracentron sinense. To identify the divers of its latitudinal adaptation, we integrated functional trait differentiation, environmental filtering, and phylogenetic conservatism. We measured 35 functional traits (leaf morphology, nutrient stoichiometry, stomatal traits, whole-plant architecture) across four natural populations spanning the species’ latitudinal range: BMXS (Baima Snow Mountain), DFD (Dafengding), FP (Foping), LGS (Leigong Mountain). Using correlation analysis, principal component analysis, and phylogenetic community metrics, we found that T. sinense dominated all communities. Populations exhibited divergent strategies: DFD expanded leaf area for light capture under high rainfall and shaded conditions; FP increased height and crown width to compete for light; LGS enhanced nutrient-use efficiency under phosphorus limitation; BMXS promoted phosphorus uptake under nitrogen limitation (N/P < 14). Trait variation correlated significantly with elevation, solar radiation, and temperature. PCA explained 90.44% of total variance, and standardized effect size (SES) values for phylogenetic signals range from −2.031 to 1.973; Phylogenetic signals were stronger in co-occurring taxa than in T. sinense. T. sinense populations in BMXS and FP are structured by competitive exclusion, while those in LGS and DFD by habitat filtering. We conclude that T. sinense achieves latitudinal adaptation by overcoming phylogenetic niche conservatism through phenotypic plasticity. While leaf economic traits remain evolutionarily conserved and niches in glacial refugium are relatively stable, populations adjust trait syndromes via metabolic shifts and structural trade-offs in response to heterogeneous environmental filters. Identifying these adaptive strategies can guide seed sourcing for restoration efforts under climate change.