Inferential analysis
ISARs were fitted using the logarithmic transformation of the Arrhenius (1921) power model. We compared the models using adjusted-R2 values as a measure of their goodness-of-fit. As the models have the same number of fitted parameters, the R2 are directly comparable, without modification (Triantis et al. 2005). We also calculated the mean area-adjusted species richness for all angiosperm and centipede chorotypes and distinguished between true and land-bridge islands. To investigate the impact of past geographical changes on current diversity, we compared the performance of three alternative generalized linear mixed models (GLMMs) in explaining species richness. The models correspond to the geographical setting of the Aegean at three stages: present-day, LGM and MSL. The present-day model (null model) consisted of present-day area, distance to the mainland, and spatial autocorrelation as fixed effect and phytogeographical province as random effect. The models for the paleogeographical settings (LGM or median) included the same predictors as the null model plus the following metrics of change in insular geography compared to the present-day setting: area loss, increase of distance to the mainland and whether an island was a land-bridge island or remained a true island. We fitted these three sets of predictors on the following response variables: the species richness of all six chorotypes of angiosperms, the total angiosperm species richness, total angiosperm endemics richness and total centipede species richness. All models were fitted using a log-link function and Poisson distribution for the error term (lmerTest package, Kuznetsova et al. 2017). All variables with p-values > 0.1 were excluded from the models to obtain a set of “suggestive, but inconclusive” predictors (Murtaugh 2014) before refitting with the remaining variables. Multicollinearity was addressed by computing the variance inflation factors (VIF) of the predictors and removing variables with VIF > 2.5 (Dormann et al. 2013). Finally, we identified the models that provided most explanatory potential using multiple measures of goodness-of-fit: the corrected Akaike Information Criterion (AICc), Bayesian Information Criterion (BIC), conditional (R2c) and marginal (R2m) R2 (MuMIn package, Barton 2009) and leave-one-out cross-validated (loocv) pseudo-R2. All analyses were performed in R version 3.4.2 (R core team 2018). Crete was excluded from all models fitted as diagnostic residual plots of residuals vs. leverage systematically designated it as an outlier (not shown). Because of the low number of endemic centipede species and their over-dispersion in the islets adjacent to Crete, we restrained our analysis of the centipede fauna to native centipede diversity.