Contemporary geography dominates butterfly diversity gradients within the Aegean archipelago (Lepidoptera : Papilionoidea, Hesperioidea)

Aim We compare the influence of contemporary geography and historical influ ences on butterfly diversity for islands in the Aegean archipelago. Location The Aegean archipelago (Greece) and two islands (Cyprus and Megist i) in the Levantine Sea. Methods Thirty-one islands were examined. Data are taken from own surveys ( Coutsis and Olivier) and from the literature. Stepwise multiple regression is used to determine relationships between species richness, frequency, rar ity and endemicity against potential geographical predictors. Stepwise logi t regression is used to determine geographical predictors of species incide nce on islands. Inter-island and inter-species associations have been exami ned using multivariate ordination and clustering techniques. Results The Aegean butterfly fauna is characterized by decreasing diversity and rarity, and increasing homogeneity, from the periphery to the present geographical centre of the archipelago (Cyclades). Diversity and rarity are shown to relate closely to species richness, and species richness, in turn , is largely explained by contemporary geography, particularly the degree o f isolation from the nearest mainland sources of Greece or Turkey, and isla nd dimensions. Islands towards the centre of the archipelago are characteri zed by a group of mobile species (n greater than or equal to 20 species) wi th extensive ranges across Europe; species that would have recolonized Sant orini (Thira) following the VI6 eruption there c. 1630 BC. Endemic componen ts, indicative of autochthonous evolutionary events, are few (5% of species are endemic) compared to known sedentary organisms (molluscs and isopods), but exceed those for more mobile animals (i.e. birds); their distribution is mainly confined to large isolated islands along the Aegean are (i.e. Kri ti) and in the Dodecanese group. Main conclusions Contemporary geography, i.e. processes currently operating in ecological time, dominates butterfly diversity gradients (species richn ess, frequency, rarity and incidence) in the archipelago. Two reasons are s uggested to account for the lack of endemism and the pattern of decreasing diversity into the Cyclades. First, relict butterfly elements may have beco me extinct on all but a few larger islands, particularly from environmental changes since the Neolithic (fire and overgrazing). Second, colonization f rom the continental landmasses is ongoing with more mobile species transfer ring even to the most isolated islands.