The Plant Diversity of Cultural Habitat Islands: Aspects of the Flora of the Mystras UNESCO World Heritage Site (Greece)

The Mystras UNESCO World Heritage Site (MUWHS) is a medieval historical area located on a small hill facing Sparta in the Mediterranean hotspot of the Peloponnese and receives a high number of visitors annually. The main aim of this study is the inventory and analysis of plant species composition and diversity of the Mystras archaeological area, with emphasis on different aspects of its flora, on the specialist endemic plants, and on the generalist ruderal and alien taxa. A high plant species richness was observed, and 321 vascular plant taxa were registered. Most of the taxa are Mediterranean or have a more widespread distribution, and half of them are ruderals. Concerning endemism, 14 Greek and 7 Balkan endemic taxa were registered. As anticipated, the most species-rich plant families recorded in the study area are Asteraceae, Fabaceae, and Poaceae. The total flora is predominantly composed of therophytes, reflecting the site’s Mediterranean climate and disturbance-adapted ecological conditions while the endemic flora is mostly composed of hemicryptophytes. Comparisons of MUWHS plant diversity with four other archaeological sites of the same floristic region of Greece, the Peloponnese, highlighted its high α-diversity on all aspects of its flora and its floristic dissimilarity from the other areas and, additionally, the high plant species richness that is comprised in all five of them. Comparisons of the flora of MUWHS with other Greek and Mediterranean archaeological areas showed significant similarities in the floristic elements considered as deteriogenic for the protected walls and monuments. The findings of our study underscore the urgent need to prioritise the sustainable conservation of archaeological sites such as Mystras. These landscapes are not only cultural monuments but also reservoirs of biodiversity and ecological value. Effective management must, therefore, adopt an integrated approach that balances the preservation of historical structures with the protection of native flora and ecological processes.