Assessment of Genetic Variability and Population Structure of Betula utilis subsp. jacquemontii in the Western...

Betula utilis subsp. jacquemontii (Spach) Ashburner & McAll. is a medicinally and ecologically important tree species in the Western Himalayan Region (WHR) of India. Estimation of genetic variability and population structure of 11 populations of B. utilis subsp. jacquemontii in the WHR were carried out using 15 ISSR and 10 DAMD markers. The cumulative analyses of the markers (ISSR + DAMD) revealed a moderate level (49.47%) of polymorphism at the species level. Khilanmarg, Gangotri, and Khaliya top populations showed the highest polymorphism, while the Bhyundar Valley and Chatru-Kaza road populations showed the lowest polymorphism across 11 populations. Mantel test revealed a positive correlation between pair-wise genetic and geographical distances in wild populations of B. utilis subsp. jacquemontii in the WHR. The AMOVA analysis showed that majority of variation of the species exists among populations (54%), followed by within populations (20%). The clustering pattern obtained from UPGMA, PCoA, and STRUCTURE analyses revealed that 11 natural populations of B. utilis subsp. jacquemontii separated into two distinct genetic clusters. The genetic differentiation is notably high (G_ST = 0.74) among populations with a low gene flow (Nm = 0.16), which could be attributed to geographic isolation, high mountain ranges, regional climatic conditions, and habitat destruction in the WHR. The genetically diverse populations recognized in this study could be a valuable genetic resource for conservation and management of this important timberline tree species.