Using floristic data to shed light on the origin of flora in the poorly studied common cypress habitats of Northern Iran.

Despite the ecological importance, there is a large knowledge gap on different habitat types of the Hyrcanian World Heritage. The Hyrcanian Common Cypress Habitats (HCCHs), the easternmost part of the Common Cypress habitats in the world, are one of these habitat types. HCCHs are understudied and threatened by a variety of anthropogenic disturbances. In the current study, synthesizing the floristic data of all HCCHs, we compared the species composition of HCCHs to 20 habitats from the Hyrcanian, Irano-Turanian, and Mediterranean regions. Also, we candidate the HCCH with the highest conservation priority by calculating the phylogenetic richness of HCCHs. The ordination analysis results showed that the HCCHs form a distinct group from the three regions. Thus, we found that the HCCHs have a unique floristic composition. The geographical distance had a weak effect on the grouping (Procrustes Sum of Squares = 0.886 and p-value < 0.001). We also detected that the phylogenetic richness of the HCCHs is highest in the Golestan National Park which is the easternmost habitat of HCCHs. Therefore, this park had the most conservation value. Our results provide new insights into the floristic composition and conservation status of the Hyrcanian World Heritage. We conclude that the bioclimatic classifications might be a better predictor of floristic compositions than biogeographical classifications. Based on the observation of Hyrcanian habitats with intermediate floristic composition, it is necessary to reconsider the biogeographical classifications of the region. Our findings are useful for developing management strategies for HCCHs.