Biogeography, land snails and incomplete data sets: the case of three island groups in the Aegean Sea

Abstract

This research aimed to study the land snails of three island groups (Skyros, Astypalaia, Kalymnos) in the Aegean Sea and the biogeographical patterns arising, with reference to the other Aegean islands. A total of 91 species was found on the 37 islands surveyed, with 89 being extant. For the majority of the islands the malacofauna is reported for the first time. Similarity indices, chorotypes and nestedness were studied for each of the island groups. The islands belonging to the same island group were clustered together, exhibiting a quite delimited malacofauna. The Mediterranean and Palaearctic elements dominate, with the Aegean element increasing in the Astypalaia group. The three island groups, despite their different geological histories and the different level of the present‐day geographical isolation, have been formed quite recently in geological time. This “recent” formation of the groups results in islands, especially the small ones, which still behave as parts of a continuous land mass. In the context of the new results from the present work, the completeness of the knowledge of the terrestrial malacofauna of the Aegean islands is discussed, and the caution needed for drawing general biogeographical conclusions based on the available data is emphasized.