Questions: The highest mountain peak of Zagros is located in the Dena mountain system (4409 m a.s.l.), which is identified as the second richest center of plant endemism of Zagros. In this study we (1) investigate floristic affinities of Dena Mts to adjacent mountain ranges based on the endemic species of the Iranian Plateau, (2) identify the species reaching the subnival zone, and (3) characterize the plant communities of the subnival zone of Dena Mts. Study area: Dena Mts is a calcareous mountain system in southern Zagros, Iran. Methods: The list of taxa endemic to the Iranian Plateau present also in Dena Mts was taken from our previously published data. Novel vegetation data were collected using the methodology of Braun-Blanquet. Classification was carried out in JUICE using the Modified TWINSPAN method. Results: Of the 242 taxa endemic to the Iranian Plateau present in Dena Mts, 22 taxa are endemic to the latter. Dena Mts have the strongest floristic affinity with the Yazd-Kerman massif, with which they share 84 taxa compared to 51 taxa shared with Alborz, 37 taxa shared with the Azerbaijan Plateau, and 15 taxa shared with Kopet Dagh-Khorassan. In Dena Mts, 38 taxa reach the subnival zone, most of them being endemic to the Iranian Plateau (68%). From scree habitats in the subnival zone, two new plant associations are described, Aethionemetum umbellati and Zerdanetum anchonioidei. These constitute a newly described alliance Galion pseudokurdici, classified within the class Didymophyso aucheri-Dracocephaletea aucheri. Conclusions: Although Dena Mts lie within a protected area, this will not prevent shrinking of alpine and subnival habitats due to global warming. Consequently, strong attention to the conservation of all range-restricted species of this mountain system, especially of alpine and subnival species, is highly recommended.<br> Taxonomic reference: Flora of Iran (Assadi et al. 1989–2021) and, for families not yet covered in the previous source, Flora Iranica (Rechinger 1963–2015).
