Edaphic Niche Differentiation Exceeds Field Ecophysiological Divergence Among Wild Rosa Species Across the Mountain Systems of Eastern Kazakhstan

Environmental heterogeneity can promote niche differentiation among closely related species, yet ecological segregation may not be mirrored by traits measured during a single field campaign. We tested whether edaphic differentiation exceeded morphological and ecophysiological divergence in Rosa acicularis, R. alberti, and R. spinosissima across the Altai and Tarbagatai Mountains of eastern Kazakhstan. The dataset comprised 40 field records representing 25 geographic coordinates and 30 species–site combinations. Plant height, crown width, chlorophyll fluorescence, chlorophyll-related outputs, and soil pH, electrical conductivity, total nitrogen, and total carbon were analysed using FDR-controlled univariate tests with Dunn post hoc comparisons, PERMANOVA, reduced-variable PCA, partial redundancy analysis, correlation analysis, and small-sample explanatory models with leave-one-out validation. Within Tarbagatai, species identity explained 48.6% of multivariate soil variation but only 9.2% of plant-trait variation. Omnibus differences in pH, nitrogen, and carbon remained significant after correction, and the species–site analysis also supported EC differentiation. The soil block explained no significant independent component of plant-trait variation after species and mountain system were taken into account. Rosa spinosissima was taller in the Altai at the observation level, and a species-plus-region model showed moderate cross-validated performance for height; models for other traits had little predictive value. These results support edaphic niche differentiation accompanied by limited divergence in field-measured traits. Because the study was observational and temporally restricted, the findings demonstrate environmental association rather than adaptation. Still, they identify testable hypotheses and support environmentally stratified conservation of wild Rosa genetic resources.