Fig. 1.

Model structure. A priori pathways were hypothesized between exogenous variables (rectangles) and endogenous variables (circles) based on arguments from the literature (see text). Three categories of taxa (green) were considered: Plants (i.e., vascular plants), Vertebrates (e.g., birds, mammals), and Invertebrates (e.g., land snails, beetles). Archipelago configuration (blue) was represented by NumIsl = Number of islands, AreaScale = ratio between the largest and the smallest islands within each archipelago, and ArchArea = total land area of the archipelago. Isolation (brown) = archipelago distance from the mainland. Diversity properties (gray) are represented by Gamma diversity = total species richness of an archipelago, and by logC, and z (i.e., the parameters of the ISAR of each archipelago). Archipelago identity (not shown) is included as a random factor because some archipelagos are represented by separate datasets for different taxa. For the full set of variables initially considered and their pairwise correlations, see SI Appendix, Table S1.