Species–area relationships of the Aegean, a comparative approach between six taxa

Abstract

Islands occupy a proportionately small area on Earth, however they play a crucial role in Ecology and Biogeography, as they constitute "natural laboratories". The increased number of species, with increasing island area, is such a commonly observed pattern that it has been labelled as one of the few laws of ecology. The Aegean archipelago is of broad biogeographical interest, as it has a considerable number of islands in addition to a rich paleogeographical and geological history, while being divided among three continents (Europe, Asia, Africa). As a result, the composition of life in the Aegean is dominated by species of European, Asian, African origin as well as species endemic in the archipelago. In this framework, we approached the species-area relationship (SAR) of the Aegean islands for six different organismic groups (birds, herptiles, snails, isopods, tenebrionids and chilopods)and 20 different models. The aim was to determine which model(s) perform better for each taxon and also to compare the z and C parameters of the power model between animal groups, which are the only model parameters to date that have been linked with biological processes.We compared the relationship across different taxa for the entire archipelago and for the exact same islands, in two subgroups with similar paleogeographic history and environmental conditions in the central and eastern Aegean. For the taxonomic groups that were examined a strong correlation between the number of species and area was found, except for chilopods and herptiles. Although there is no universal best model for the SAR of the Aegean, the power model performed better for invertebrates, whereas concerning vertebrates there was more ambiguity in the shape of the relationship. Highlights• We provide a comparison of the species-area relationship for 6 different animal groups in an archipelago that mostly comprises of continental islands.• Snails and isopods display the highest C values within the power model species-area models.• Herptiles seem to have in general the lowest C and highest z values which could be mainly attributed to their small overall species number and generally low dispersal ability, respectively.• Species-area models that perform best for a specific taxon in a subset of islands do not necessarily explain the data adequately for the entire archipelago and vice-versa.