Spatial patterns of diversity in the tenebrionid beetles (Coleoptera, Tenebrionidae) of the Aegean Islands (Greece)

Question: How do present and historical factors influence beta and gamma diversity of strictly resident animals on a land-bridge archipelago? Data description: Islands were characterized in terms of present geography, shape, area size, habitat diversity and paleogeography. Diversity patterns are based on 170 tenebrionid taxa from 32 islands (Greece). Search method: The influence of present eco-geographic variables on gamma diversity (species numbers) was assessed using pairwise correlations, multiple regressions and path analysis. Canonical correspondence analysis was applied to study the influence of present and past island characteristics (represented by multidimensional spaces) on beta diversity (calculated as biogeographic similarity among islands). Fuzzy analysis was applied to determine island groupings based on beta diversity. Conclusions: Larger islands have more species because they have more habitats. Distance and shape effects were small. Thus present colonization processes do not play a substantial role. Tenebrionids colonized the islands by Pleistocene land-bridges. Larger islands retained more species. Beta diversity was moulded mostly by paleogeographic conditions. The Aegean Islands were subject to a twofold colonization process. Relatively few species have been able to cross the middle Aegean sea barrier to colonize islands far from their mainland source.