| Abstract |
This study took place at the Natural History Museum of the University of Crete, Department of Biology, from June 2002 to November 2003. It is based on publications concerning the flora and vegetation of the majority of the South Aegean Arcs islands, as well as of the islands Symi and Tilos, located on the northern part of Rhodes and belonging to the East Aegean. Its subject was the study of the area from the point of view of Theory of Island Biogeography. This approach is actually original, compared to the accumulated knowledge on the islands flora and vegetation and the phytogeographical relationships of the islands with the neighboring mainland. The purpose of this study is in particular the examination of the plant species area relationship on the South Aegean island Arc. In addition, this study tried to embody the concept of plants' habitat in this phytogeographical study. The species - area relationship in its double logarithmic form (logA logS), as the pattern used by most biogeographers today, was applied for the area and flora of 48 Arcs islands and islets, the islands and islets separately, for various subgroups of the 48 islands, ten selected plant families, three ecological groups and the woody species. The z-value for the 48 islands and the whole flora lays in the range indicating island groups and continental, moderately isolated islands. Thus, this result is in accordance with the geological history of the study area. However, the z-value is high, indicating that the islands perform in a different way and do not comprise parts of a united phytogeographical region. The great number of islets included in the analysis of the 48 South Aegean Arcs islands influences significantly the slope of the logA logS straight line, causing its increase. When the same analysis is performed only for the great islands, the z-value decreases significantly. The small number of common plant species among great and small islands contributes to the faster increase in the species number, so that the z-value is high. The logA logS pattern, as far as the slope z and the intercept c are concerned, changes according to the island or the plant group analyzed each time. The results of our analysis indicate that there is a greater phytogeographical relationship between the islands in Karpathos island complex and the west (Cretes island group) than the east (Rhodes' island group). There is evidence of small island effect for 38 of the 48 islands, a grouping with a certain phytogeographical significance, only if the semi-logarithmic form of the model is used. It was rather difficult to determine the habitats, because a large number of physical parameters can be used, so that it is practically possible to specialize the description of the habitat of a plant species or of a group of plant species to the level at which the researcher aims. The use of "Choros" model and the path analysis, applied for plant habitats on seven islands and for vegetation types on 37 islands indicates that the area plays the most significant part in the determination of the plant species number on Arc's islands.
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