Phylogeography of Tenebrionid beetles in the Aegean archipelago

Abstract

The Aegean archipelago, which has a mostly continental origin, provides a ‘natural laboratory’ to explore the effects of dispersal limitation on population and community structure. This thesis investigated the phylogeographic, genetic diversity and species richness patterns of the darkling beetles (Coleoptera: Tenebrionidae) of the central Aegean islands. Sampling was conducted on 30 islands and the corresponding coasts of Greece and Turkey and several individuals per taxon and locality were sequenced for mitochondrial and nuclear markers. The generated sequence data were used to: reconstruct phylogenies, calculate population genetic parameters, apply DNA-based species delineation methods, estimate substitution rates and assess macroecological patterns. The results show that many of the existing taxonomic names do not reflect the genetic diversification processes in the archipelago. The majority of the morphological species are split into several geographically confined clades, recognised as ‘independently coalescing entities’. Habitat preference and wing development were identified as two major factors affecting phylogeographic structure, genetic diversity and macroecological patterns. Differences in dispersal propensity were observed between psammophilic taxa inhabiting ephemeral coastal sandy habitats and geophilic taxa associated with presumably stable compact-soil habitats. The widespread geophilic lineages were found to be deeply subdivided along the biogeographic barrier of the ‘mid-Aegean trench’, and the age of this geological event was used as a calibration point to estimate substitution rates and reassess the ‘standard' insect mitochondrial molecular clock. A positive species – genetic diversity correlation was recorded, driven primarily by island sizes and geographic distances, while certain macroecological regularities such as the species – area curve and the distance – decay of similarity relationship could be described at both species and haplotype level. This study demonstrated how palaeogeography, contemporary geography and habitat persistence interact with stochastic processes at population and community level to shape the observed diversity patterns of the Aegean tenebrionid fauna.