Two new grassland associations from the Madonie Mountains (Sicily) disclose critical classification issues in endemic-rich oromediterranean plant communities of the classes Molinio-Arrhenatheretea and Rumici-Astragaletea siculi

This study deals with the phytosociological classification of the grassland plant communities of the Madonie Mountains (Sicily, Italy). We combined data from 185 vegetation plots obtained from scientific literature, with 42 plots sampled, in summit areas above 1900 m a.s.l. Only vascular plants were recorded, and soil samples were collected to analyse the main substrate parameters. Using the TWINSPAN classification, 15 clusters were identified, interpreted and classified at the association level. Four distinct vegetation units were recognized: (1) mesohygrophilous and subacidophilous meadows, (2) gorse vegetation dominated by pulvinate chamaephytes and hemicryptophytes on wind- swept ridges, (3) petrophytic vegetation on eroded soils, and (4) grasslands on slopes of carbonate rocks soils. Two newly described associations, Androsaco breistrofferi-Potentilletum calabrae (Cl.: Molinio- Arrhenatheretea, Ord.: Cirsietalia vallis-demonis, All.: Plantaginion cupanii) and Helianthemo tomen- tosi-Festucetum crassifoliae (Cl.: Rumici-Astragaletea siculi; Ord.: Erysimo bonanniani-Jurinetalia bocconei; All.: Cerastio tomentosi-Astragalion nebrodensis), occupy the highest elevations and exhibit unique ecological features: temperature and water potential data revealed differences between these two communities, with the former thriving in sinkholes (karst dolines) with long-lasting snow cover and extended water availability, while the latte withstands fluctuations in temperature and water avail- ability on windy ridges. Significant differences in topography and soil properties occurred between the new associations. Finally, we highlighted the classification challenges existing at higher hierarchical levels within the studied communities of the Molinio-Arrhenatheretea and Rumici-Astragaletea siculi, emphasising the need to address these issues beyond the Madonie Mountains to encompass the broader Mediterranean region.