ORIGINAL ARTICLE Network biogeographical analysis of the central Aegean archipelago Konstantinos Kougioumoutzis 1 *, Stylianos Michail Simaiakis 2 and Argyro Tiniakou 1 1 Department of Biology, University of Patras, GR-26500 Patras, Greece, 2 Natural History Museum of Crete, University of Crete, Knossos Avenue, Heraklion GR-71409, Crete, Greece *Correspondence: Konstantinos Kougioumoutzis, Department of Biology, University of Patras, GR-26500, Patras, Greece. E-mail: konkougioumou@upatras.gr ABSTRACT Aim Although the factors shaping plant species richness patterns across the islands of the central Aegean are well known, the processes driving the assem- bly of these island communities remain unclear. To shed light on these pro- cesses, we identified biogeographical modules within the phytogeographical area of the Cyclades and tested for nestedness across the islands. Location The Cyclades, Greece. Methods We used a network approach to detect island biogeographical roles and modules, based on a large and detailed database of the Greek endemic plant taxa of the Cyclades, and we tested for nestedness in the island–species matrices. Results The Cyclades were significantly modular and divided into five biogeo- graphical modules. Three of the modules were significantly nested and two dis- played all four possible biogeographical roles (connectors, module hubs, network hubs, peripherals). Most of the network’s taxa are classified as peripherals and widespread endemics. Main conclusions The borders of the five modules correspond remarkably well to the palaeogeographical and climatic compartmentalization of the Cyc- lades. The flora of the Cyclades has not yet reached the relaxation phase and the region may act as an ecogeographical filter for the distribution of several plant lineages. Naxos, Milos and Anafi play an important role for the network’s connectivity, while at least five adjacent phytogeographical regions affect the distribution patterns of the endemic taxa present in the Cyclades. Keywords Colonization routes, connectance, Cyclades, dispersal, ecological network, endemism, island biogeography, modularity, nestedness, palaeogeography. INTRODUCTION The Aegean Sea has long attracted the attention of biogeog- raphers (Turill, 1929; Strid, 1996) because of its high envi- ronmental and topographical heterogeneity (Blondel et al., 2010), diversity and endemism (Strid, 1996). The Aegean Sea contains more than 7000 islands and islets (Triantis & Mylo- nas, 2009) of various sizes. Plant distributional origins are, in general, well known (Strid, 1996) with elements originating from three different biogeographical regions, namely Europe, Asia and Africa (Strid & Tan, 1997). Turill (1929) was the first botanist to divide Greece into 12 phytogeographical regions, while Rechinger (1943, 1950) laid the foundations of the prevailing phytogeographical subdivi- sion of the Aegean. Strid (1996), based on Rechinger (1943, 1950), divided Greece into 13 phytogeographical areas. Rech- inger & Rechinger-Moser (1951), Runemark (1970) and Gre- uter (1970, 1971) were the first phytogeographers to address the distributional and floristic problems arising from the pal- aeogeographical history of the Aegean Sea. The distributional patterns of plant groups in the Aegean Sea may reflect palaeogeographical patterns or historical events (Comes et al., 2008, and references therein). The effect of vicariance events, restricted gene flow and genetic drift in shaping the distribution of the genetic diversity of the Aegean archipelago’s flora has also been examined (i.e. Cellinese et al., ª 2014 John Wiley & Sons Ltd http://wileyonlinelibrary.com/journal/jbi 1 doi:10.1111/jbi.12342 Journal of Biogeography (J. Biogeogr.) (2014)