Ecological, Anatomical, and Genomic Insights into the Rare Tree Species Fraxinus sogdiana, Celtis caucasica, and Betula jarmolenkoana from the Northern Tien Shan

This study provides a comprehensive assessment of the population structures, anatomical adaptations, and chloroplast genome organizations of three rare tree species—Fraxinus sogdiana Bunge, Celtis caucasica Willd., and Betula jarmolenkoana Golosk.—from the Northern Tien Shan region of Kazakhstan. Field surveys revealed species-specific demographic patterns, with F. sogdiana and B. jarmolenkoana populations displaying a complete age spectrum and signs of ongoing regeneration, while C. caucasica exhibited a lack of juvenile stages, indicating regeneration failure. Anatomical analysis of leaf and stem tissues highlighted adaptive features aligned with habitat conditions: F. sogdiana showed mesophytic traits suited for riparian environments, C. caucasica displayed xeromorphic structures reflecting drought tolerance, and B. jarmolenkoana demonstrated structural reinforcement adapted to high-altitude stressors. Whole chloroplast genome sequencing revealed conserved quadripartite architecture across species, with minor variations in gene content and inverted repeat boundaries suggesting lineage-specific evolution. The findings underscore the ecological sensitivity and conservation priority of these species and provide foundational data for future ecological monitoring, restoration efforts, and phylogenomic research in Central Asian montane ecosystems.