Integrative Assessment of Morphological, Leaf-Anatomical, Edaphic, and DNA-Barcode Variation in Sibiraea altaiensis (Laxm.) C.K.Schneid. and Sibiraea tianschanica (Krasn.) Pojark. from Kazakhstan: Implications for Sustainable Conservation

Mountain ecosystems of Kazakhstan host geographically isolated Sibiraea populations, whose taxonomic status is complicated by overlapping morphology, environmental plasticity, and conflicting nomenclatural treatments. We compared 177 adult shrubs sampled at nine elevation-stratified sublocalities nested within three regional analytical groups (two S. altaiensis groups, n = 60 each; one S. tianschanica group, n = 57) using whole-shrub morphology, quantitative leaf anatomy, four soil variables, and a preliminary four-locus DNA-barcode comparison based on eight taxon-level consensus sequences (two taxa × four loci). One-way ANOVA identified regional-group differences in bush width (F(2,174) = 8.89, p < 0.001), vegetative offshoot number (F(2,174) = 21.85, p < 0.001), leaf-blade thickness (F(2,174) = 21.09, p < 0.001), soil pH (F(2,174) = 72.61, p < 0.001), electrical conductivity (F(2,174) = 41.22, p < 0.001), total nitrogen (F(2,174) = 40.21, p < 0.001), and total carbon (F(2,174) = 39.00, p < 0.001). In contrast, plant height and several vascular traits did not differ significantly, and most soil-trait associations were weak (| ρ | ≤ 0.33). Across ITS, matK/KIM, psbA-trnH, and rbcL, the concatenated alignment showed 99.49% identity and an uncorrected p-distance of 0.51%; psbA-trnH (0.97%) and ITS (0.69%) were the most variable loci. The combined evidence demonstrates regional phenotypic and edaphic differentiation but does not establish independent evolutionary lineages because taxon and geography are confounded, and individual-level genetic variation was sparsely sampled. By establishing measurable baselines for demographic monitoring, habitat protection, provenance-based ex situ conservation, and future restoration, the study directly supports the sustainable management and long-term resilience of rare mountain-plant populations in Kazakhstan.