Evolutionary Imprints on the Foliar Elementome: Biogeochemical Niche Differentiation Among Fagus Species

ABSTRACT Although phylogenetically related plant species often differ in competitive ability, the underlying causes remain poorly understood. The present study characterizes the biogeochemical niches (BN) of Fagus species to clarify interspecific variation in elemental acquisition, life history strategies, and competitive abilities. Quantifying the biogeochemical niche (BN) provides a mechanistic framework to address the shortfall in our understanding of how evolutionary history shapes trait–environment relationships and governs interspecific competition. We examined Fagus grandifolia Ehrh. from North America, Fagus sylvatica L. from Europe, and Fagus crenata Blume. from Asia. Foliar N, P, K, Ca, and Mg concentrations and nutrient ratios data from 328 sites found in published data were analyzed in relation to climate data. Multivariate analyses identify distinct foliar chemical signatures for each species. Phosphorus (P) and calcium (Ca) significantly differentiated F. sylvatica from its congeners ( p < 0.001), while F. crenata exhibited the highest concentrations of K and Mg ( p < 0.001). Squared Mahalanobis distances confirmed a clear elementome (the chemical‐atomic stoichiometrical composition) separation, with F. sylvatica and F. crenata representing the most divergent biogeochemical niches. Discriminant analysis (FDA) correctly classified > 85% of samples based on species foliar atomic composition identity, with phosphorus (P) and calcium (Ca) being the primary drivers of differentiation. Our results reveal that these congeners occupy non‐overlapping biogeochemical niches, suggesting that their respective elementomes are deeply conserved traits shaped by ancestral climate and edaphic conditions. Functional profiling reveals three distinct syndromes: F. grandifolia adopts a conservative, resource‐use‐efficient strategy; F. sylvatica exhibits a stoichiometrically flexible, acquisitive strategy consistent with its rapid post‐glacial expansion; and F. crenata displays an intermediate, plastic strategy. These findings indicate that competitive dominance and forest resilience in Fagus are underpinned by species‐specific elementomes. Consequently, climate‐driven shifts in species composition will fundamentally restructure ecosystem‐level nutrient cycling and stoichiometry.