Serpentine soils host a large number of endemic species and contribute to the turnover of community composition. The infertility of the soil strongly influences the species and functional composition of serpentine environments. Plant communities in environmentally harsh habitats such as serpentine soils may demonstrate unique responses to environmental change, via the mediating role of their functional traits. The Khorassan-Kopet Dagh floristic province located in the northeastern region of Iran has a high level of plant endemism due to its biogeographical position as well as the large extent of calcareous, gypsum, and ophiolitic soils. To gain a better understanding of the impact of environmental conditions on serpentine plant communities in the area, we sampled 44 relevés using the Braun-Blanquet method at two sites dominated by two threatened, endemic and phylogenetically closely related Cousinia species (Cousinia sect. Argenteae) in serpentine soils of NE Iran, i.e., Cousinia kadereitii and C. argentea. The adaptive strategies of two Cousinia communities were investigated according to Grime’s competitor/stress-tolerator/ ruderal (CSR) model. While both plant communities occupied similar habitats ecologically and converged on the stress-tolerator strategy, C. kadereitii exhibited functional divergence from C- to S-selected, however, C. argentea showed functional convergence on the S-selected strategy. Understanding the strategies employed by different species can give us valuable insights into the resilience and survival of plant communities in challenging environments. This knowledge is crucial for biodiversity conservation efforts in serpentine habitats.

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