Community variation of spiders, beetles and isopods in three small island groups of the Aegean Sea: the interplay between history and ecology

Abstract

Aim To study the variation in the species turnover and nestedness components of compositional dissimilarity in a multi‐taxa and multi‐island‐group system. In addition, to examine the influence of several biogeographical drivers on compositional dissimilarity and discuss the findings in the light of the ecological characteristics of taxa and the palaeogeographical histories of island groups. Location A small‐scale system of island groups within the Aegean Sea, namely the Astypalaia, Kalymnos and Nisyros groups, with different palaeogeographical histories. Methods We examined community variation of predatory ground spiders, omnivorous ground beetles and detritivorous terrestrial isopods. Compositional dissimilarity was decomposed for each group, by disentangling all compositional differences (β total ) into two components, species turnover (β jtu ) and nestedness (β jne ). Partial Mantel tests were used to test the effects of island area, island elevation and inter‐island distances on β jtu and β jne . Results Compositional dissimilarity levels of all arthropod communities varied among island groups and were primarily dominated by the species turnover component of compositional dissimilarity. Species turnover of spider communities was lower within the old and isolated Astypalaia group compared to the younger and less distant from mainland Kalymnos and Nisyros groups. Elevation differences between islands did not affect compositional dissimilarity. In contrast, area and inter‐island distances significantly affected compositional dissimilarity between islands, albeit only in island groups of continental origin and only in some of the examined arthropod groups. Main conclusions Despite their geographical proximity, the three island groups show differences in compositional dissimilarity patterns which are more pronounced in the predatory arthropod communities. Using multiple taxa and clearly defined palaeogeographical and topographical elements, i.e. island groups, we show that the ecological characteristics of organisms and idiosyncrasies in geography and palaeogeography can be reflected in compositional dissimilarity patterns at small geographical scales.

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