A syntaxonomical survey of the Sicilian dwarf shrub vegetation belonging to the class Rumici-Astragaletea siculi

Basing on literature data and unpublished relevés from Sicily, a survey of the syntaxa belonging to the class Rumici-Astragaletea siculi Pignatti & Nimis 1980 em. Mucina 1997 (= Cerastio-Carlinetea nebrodensis Brullo 1984) is presented. The class groups orophilous plant communities dominated by dwarf- shrubs, often with a pulvinate and thorny growth form. The class is represented in Sicily by two orders: Rumici-Astragaletalia siculi Pignatti & Nimis 1980, including the sole alliance Rumici-Astragalion siculi Poli 1965, restricted to Mount Aetna, and Erysimo-Jurinetalia bocconei Brullo 1984, including two alliances: the acidophilous Armerion nebrodensis Brullo 1984 and the basiphilous Cerastio-Astragalion nebrodensis Pignatti & Nimis ex Brullo 1984. Within the class, nineteen associations have been recognized. Nomenclature, floristic settlement, ecology and chorology are examined for each syntaxon. The floristic autonomy of the class Rumici-Astragaletea siculi is examined from the phytogeographic viewpoint and is confirmed by numerical analyses including not only the Sicilian phytocoenoses, but also those occurring in Sila and Aspromonte (Calabria) and ascribed to the same class by Brullo, Scelsi & Spampinato 2001 and Brullo, Gangale & Uzunov 2004. It is, as well, highlighted that the Pollino massif represents the southernmost limit to the distribution range of the class Festuco-Brometea, whose southward expansion is hampered by the lack carbonatic highlands in the southernmost tip of the Italian Peninsula.