Habitat Islands on the Aegean Islands (Greece): Elevational Gradient of Chasmophytic Diversity, Endemism, Phytogeographical Patterns and need for Monitoring and Conservation

The Aegean archipelago, characterized as a natural laboratory for research concerning plant species diversity and phytogeography has a complex geological and paleogeographical history that varies among its phytogeographical areas. A different combination of factors of variable intensity and duration time drives patterns of its impressive plant species richness and endemism. Cliffs, a conspicuous feature of the Aegean landscape, consist of biologically closed communities that serve as refugia for obligate chasmophytes, the majority of which are Greek or Aegean endemics, and for this reason, they are also considered as habitat islands on the Aegean islands. A synoptic analysis is presented concerning chasmophytic plant diversity focusing on endemic obligate chasmophytes. Phytogeographical patterns of obligate chasmophytes, and especially the endemic ones as well as their elevational range and distribution and zeta diversity, are analyzed and discussed in the frame of climatic change, mentioning that the most threatened endemic obligate chasmophytes are those specialized in high elevation areas, and focusing on the need for monitoring and conservation.