Drought effect on the diversity of Fagus orientalis L. populations using microsatellite molecular markers and peroxidase isoenzyme

Fagus orientalis is one of the most important broadleaf species in Hyrcanian forests. The phenotypic and genetic adaptation potential of this species to climate change is very important. Quantifying and evaluating genetic diversity between and within oriental beech populations makes it possible to best preserve the diversity of populations. This study was conducted on mature trees of four different populations (regions) of this species in two drought index gradients from West to East and lowland to highland in Hyrcanian forests (Shafarood forest of Gilan, Khairudkenar forest of lowland and highland of Mazandaran and Shast Kalateh forest of Golestan). Genetic diversity was studied in native populations using seven microsatellite markers and one biochemical marker. The results showed high diversity in all populations, especially in the population of Shast Kalateh, Golestan. The results of molecular analysis of variance with SSR microsatellite marker showed that 77% of the total diversity was within populations and 23% was among the populations. The results of this study showed that the presence of more genetic diversity within the beech populations of Hyrcanian forests indicates their strong genetic basis for adaptation to environmental conditions and may facilitate short-term adaptation to climate changes. On the other hand, the presence of higher genetic diversity in Shast Kalateh than in other regions indicates stronger evolutionary forces for adapting trees to environmental conditions. Additionally, higher gene flow among allogamous populations of oriental beech has led to low genetic differentiation between populations in the drought index gradient of Hyrcanian forests.