The vegetation of islets in the Aegean and the relation between the occurrence of islet specialists, island size, and grazing
Bergmeier, Erwin; Dimopoulos, Freiburg; Dimopoulos, Panayotis
The phenomenon of 'islet specialists' has received much attention in plant geographical literature on the Aegean. Islet specialists occur chiefly on small uninhabited islands about 0.1 to few hundred hectares small. A list of islet specialists is presented, and their distribution in the Aegean is outlined. For 56 islets, the relation between the occurrence and proportion of islet specialists and parameters such as island area, altitude, and grazing is calculated. The species-area relation increases with grazing, and the proportion of islet specialists decreases. The high species numbers of grazed islets are chiefly due to annual species of phrygana habitats. The species composition of 30 South Aegean islets, which were ordinated by Correspondence analysis and Canonical correspondence analysis, suggests that grazing is more relevant to explaining the variance of the data than island size. Islet floras are neither uniform nor randomly composed, but reflect environmental (limited area) or geographical variation (wider area). A classification of 111 releve´s with islet specialists from 26 small islands throughout the Aegean (except the Kiklades) revealed 10 plant communities, which are briefly outlined in terms of species composition, ecology and distribution. The most prominent vegetation is that of coastal rocks (Crithmo-Staticetea) and halo-nitrophilous scrub (Pegano-Salsoletea). In the Aegean, the Pegano-Salsoletea vegetation seems to be more diverse and variable on islets than along other coasts. For most units, formal description as associations was considered premature, but the syntaxonomy is discussed and some nomenclaturally insufficient names from literature are validated or corrected.