Pistacia atlantica subsp. kurdica (PAK) is both an economically and ecologically keystone tree species of semi-mountainous and semi-arid forests in western and southern Iran; however, its standing genetic diversity is increasingly threatened by a range of pressures such as climate change and anthropogenic landscape degradation. To support the development of suitable conservation and management plans for this species, the geographic pattern of phenotypic and genetic variation of 33 populations (a total of 567 trees), along the climate gradient of the species natural distribution in Iran from the temperate to dry-warm forest, was examined using six phenotypic traits and 13 nuclear microsatellite markers. We found signifcant phenotypic variation in all traits and populations along with the shifting climate and observed smaller leaves but larger and heavier seeds in the dry-warm southern populations. Based on neutral SSRs analysis of genetic variation in the nuclear genome, although the current PAK populations have maintained moderate to high levels of genetic diversity (HE=0.566–0.711) to date, the populations inhabiting degraded localities in southern Zagros forests maintained lower levels of genetic diversity statistics as compared to the germplasm from the northern landscape of these forests. In addition, populations have shown a high degree of genetic diferentiation (FST=0.291) which can mostly be explained by the scattered and fragmented patterns of PAK distribution in the Zagros forests and the geographical barriers to the genetic material exchange between populations. STRUCTURE analysis revealed a geographical genetic structure and clustered populations into fve main clusters corresponding to the northern, central, and southern populations, demonstrating substantial variability across the species’ range in the values of environmental drivers shaping the composition of the populations’ genome. Finally, the Mantel tests for correlation among population matrices detected signifcant positive correlations between genetic and both geographic and climatic distances. These fndings are expected to provide theoretical support for the management and conservation designs of the PAK genetic resources in the Zagros mountains.
