The Hyrcanian forests are recognized as one of the most important biodiversity reserves in the world and provide unique habitats for endemic species such as Quercus castaneifolia. These forests, as climatic refuges during the Ice Age, have provided stable habitats for valuable species and played a crucial role in preserving the remaining species from that era. The present study aimed to model the habitat of Q. castaneifolia across the entire Hyrcanian forests and investigate habitat changes of this species in the eastern part of Mazandaran over the past two decades, along with examining the genetic diversity pattern of Q. castaneifolia in northern Iran, to provide the necessary information for developing effective conservation strategies. First, suitable habitats for Q. castaneifolia across the Hyrcanian forests were modeled using species presence data and three models (GLM, GBM, and MaxEnt) in R software, which led to the identification of areas with the highest habitat suitability. Based on the results and field visits, the eastern part of Mazandaran was selected as a region with dominant Q. castaneifolia coverage for further investigation. In this stage, using collected data and MaxEnt software, suitable habitats for this species were identified. Then, using object-based analysis, suitable oak habitats were divided into homogeneous units based on spectral and topographic characteristics to be used for identifying distribution and examining thinning operations of Q. castaneifolia trees. The comparison of the annual mean NDVI index in each unit over the past two decades (2002–2022) was calculated as a criterion for thinning. The results showed that more than 80% of the units have undergone various levels of thinning over the past two decades. Additionally, multiple linear regression analysis (P-value < 0.001) indicated that three factors road access, slope, and elevation are positively associated with thinning levels. Genetic analysis was performed using 11 nuclear microsatellite markers (nSSR) and four chloroplast markers (cpSSR). Genetic diversity indices were calculated using SPAGeDi software, and the genetic structure of populations was eva‎luated using STRUCTURE software. The effective number of alleles (Na) in different populations ranged from 4 to 6, and the observed heterozygosity (Ho) in different regions varied between 0.42 and 0.48. Additionally, the highest allelic richness (Ar) and genetic diversity were observed in the Gilan population. The results showed that expected heterozygosity (He) values did not differ significantly among populations, and the inbreeding coefficient (Fis) in all populations indicated no significant inbreeding. STRUCTURE analysis based on chloroplast markers confirmed the existence of at least two distinct genetic clusters. The results of this study demonstrated that the Hyrcanian forests, due to their unique ecological characteristics and key role in preserving biodiversity, require special conservation. Habitat modeling of Q. castaneifolia identified that large areas of the Hyrcanian forests have high habitat suitability, but destructive human impacts have led to the decline of this species in recent decades. Furthermore, genetic analysis revealed that despite high genetic diversity in populations, extensive gene flow has reduced genetic differentiation. These findings highlight the importance of precise planning for conservation management and restoration of this valuable species and provide a suitable basis for developing sustainable strategies.

منصوره ملكيان

اوليور گايلينگ , كامران پورمقدم

محمدرضا اشرف زاده , محسن احمدي , مجيد طالبي