Species richness data
We compiled a plant matrix for 70 Aegean islands, including a total of 3246 native vascular plant taxa (species and subspecies). The angiosperms are a well-studied group in the Aegean, and we compiled data on five chorotypes and two combined chorotypes (Figure 1) based on an extensive bibliographical database for the Aegean archipelago (see Appendix S1 in Kougioumoutzis et al. 2017). The ‘native non-endemics’, here termed ‘natives’, are a widely spread taxonomic group that occur both on the Greek Islands and on the mainland across the Mediterranean (2673 taxa).
The ‘Greek endemics’ are species exclusively occurring both on the Greek mainland and the Aegean islands (689 Taxa). The ‘Aegean endemics’ (AE) are found on multiple islands but not on the mainland (91 taxa). The ’phyto-region endemics’ (PE) are restricted to one or multiple islands located within the same Aegean phytogeographical region sensuStrid and Tan (1997 - 384 taxa). Finally, the single island endemics (SIEs), are endemics occurring exclusively on one of the Aegean islands (292 taxa). We also combined chorotypes to compare general trends of endemics with non-endemics and to assess trends in similar multiple endemics chorotypes. We combined both phyto-region and Aegean endemics to form ‘multiple islands endemics’ (MIEs) sensu stricto (450 taxa). We also combined all endemic chorotypes into an “all-endemics group” (EALL).
A similar matrix was compiled for 56 Aegean islands and 70 centipedes (see Simaiakis et al. 2004, 2005). Two chorotypes were distinguished: ‘native’ and ‘endemics’ (65 and 5 species, respectively). The data set for single island endemics of centipedes was too small for a statistical assessment.