Genetic Diversity, Population Structure, and Environmental Influences in Nepeta glomerulosa: Implications for...

This study provides the first comprehensive assessment of the genetic diversity, population structure, and evolutionary history of Nepeta glomerulosa, a semi-endemic medicinal plant of the Irano-Turanian region with numerous therapeutic uses. Using sequence-related amplified polymorphism (SRAP) markers, we analyzed 188 accessions from 18 populations across Iran's major mountain ranges: Alborz, Zagros, and Khorassan-Kopet Dagh. A total of 251 bands were amplified, of which 99.20% (249) were polymorphic. The species exhibited moderate genetic diversity (Nei's gene diversity index, He = 0.2605), with the highest diversity observed in the Alborz range, suggesting it may be the center of origin. Genetic differentiation among populations (Gst = 0.4199) was substantial, with analysis of molecular variance (AMOVA) revealing that 30.17% of the total variation was attributable to differences among populations, while 69.83% was due to variation within populations. Clustering analyses using UPGMA and principal coordinate analysis (PCoA) classified the accessions into two primary clusters, whereas Bayesian STRUCTURE analysis identified three distinct genetic clusters with significant admixture, particularly in populations from the Zagros Mountains. This pattern indicates that the Zagros range may function as an important zone of genetic exchange between northern and southeastern populations. Spatial and environmental variables, including geographic distance, altitude, and edaphic conditions, significantly contributed to the observed genetic structure. Field observations further indicate that N. glomerulosa populations are threatened by overgrazing, habitat degradation, and unsustainable harvesting. Considering its restricted distribution and small population sizes, targeted conservation actions are urgently required, especially in vulnerable mountainous regions.