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A dramatic insect decline has been documented on the grasslands and forests of European or North American mainland. Yet, other parts of the world and other ecosystems remain much less studied with unknown patterns.Using a unique time‐series dataset, we investigate recent trends on abundance and richness of arthropods sampled in Azorean native forest over 6 years (2013–2018).We test the hypothesis that biodiversity erosion drivers are changing the diversity and relative species abundance structure (species abundance distribution, SAD) of endemics, native non‐endemics and exotic species over time. We also examine temporal trends in abundance for each individual species.In contrast with mainland studies, we observed no decline in overall arthropod diversity, but a clear increase in the diversity of exotic arthropods and some evidence of a tendency for decreasing abundance for some endemic species. We also document stronger species turnover for exotic species, but no specific changes in the SAD.We argue that many changes, particularly in unique systems such as islands, will be noticed not at the richness but mostly at compositional level. Special attention should be given to exotic species which are known to be one of the major drivers of biodiversity erosion on islands. [ABSTRACT FROM AUTHOR]

The objective of this study was to obtain a biogeographical perspective on the hoverfly genus Merodon (Diptera, Syrphidae) based on data from 32 islands in the Aegean and Ionian archipelagoes vis-à-vis the adjacent mainland. In this part of the world, the genus comprises 57 species, out of more than 160 species described worldwide., The importance of eco-geographical variables (area, elevation, distance to the nearest island and distance to the nearest mainland) and the species-area relationship ( SAR) were studied in order to explain patterns of species richness. All tests supported the dynamic equilibrium concept., The area and distance to closest island were found to be the most important drivers of species richness on the Aegean and Ionian archipelagoes. Out of three SAR models evaluated in this study, the exponential function fitted our data best. It was found that a power model with no intercept value ( C = 1) performed even better by using symbolic regression for non-linear equation optimisation., The cluster and null-model analyses performed to detect inter-island similarities and origins of the insular Merodon fauna indicated a clear influence of colonisation history of the species on different islands., The results imply that the current distributions of Merodon species in the study area exhibit the combined effects of historical and present-day processes. [ABSTRACT FROM AUTHOR]