Conservation Hotspots of Quercus castaneifolia Revealed Through the Integration of Genetic Diversity and Landscape...

Quercus castaneifolia C.A. Mey., a dominant and ecologically important oak species in the Hyrcanian forests of northern Iran, is experiencing rapid decline due to climate change, anthropogenic pressures, and severe habitat fragmentation. This study aims to delineate genetic diversity patterns and identify key conservation areas for Q. castaneifolia across its entire range within Iran. We integrated population genetic analyses with landscape connectivity modeling to identify regions of high evolutionary and ecological importance. Using 14 polymorphic nuclear microsatellite (nSSR) and four chloroplast microsatellite (cpSSR) loci, we assessed 235 individuals across the species' geographical distribution. Nuclear markers revealed high genetic diversity (H _e = 0.54) and weak differentiation (F _ST = 0.019), suggesting extensive pollen flow, while cpSSRs showed strong spatial structure and restricted seed dispersal. Seven distinct chloroplast haplotypes were identified, with the Talesh-Mardab hydro-region exhibiting the highest haplotype diversity and harboring four private haplotypes. Habitat connectivity analysis using UNICOR revealed two main core areas located in the western (Talesh-Mardab) and eastern (Qarasu-Gorgan) Hyrcanian regions, connected by a central corridor through Lahijan-Nur and Haraz-Naka. These spatial patterns closely overlapped with areas of haplotype diversity, highlighting them as conservation hotspots. Our nuclear SSR results are consistent with previous findings showing low differentiation and extensive pollen flow, whereas cpDNA markers provided additional insights into seed dispersal and spatially structured haplotype variation. Our integrated approach provides a valuable framework for identifying core populations and genetic diversity hotspots, as well as for preserving gene flow pathways essential to the species' long-term persistence and its dynamic gene conservation.