Quediini Rove Beetles Across the Holarctic - Taxonomy, Phylogenetics, and Biogeography

The thesis is a collection of papers (published, in press, or in preparation) that target rove beetles, mainly within the Holarctic tribe Quediini, which contains more than 800 described species. Papers or work in progress are organized in five chapters. The first chapter includes two published alphataxonomic papers devoted to poorly known species groups of hypogean Quedius in Asia. Theyinclude literature reviews, descriptions of new species, new synonymy and elements of integrative taxonomy that use morphology and DNA-barcoding. Taxonomic investigation of the highlyhomoplastic hypogean Quedius clearly demonstrates the need for the rigorous phylogeny as a baseline for systematic and other studies. As an acknowledgement of that, the second chapter is a major cross-disciplinary phylogenomic paper that, in particular, has helped to elucidate the independent origin of various species groups of Quedius with hypogean biology. This paperreconstructed a phylogeny of the mega-diverse tribe Quediini and among other findings made it clear that both the nominative subgenus Quedius sensu stricto and the genus Quedionuchus would serve as good models for exploring various aspects of Holarctic biogeography. Both groups were systematically revised and a large revision of the subgenus Quedius sensu stricto formed the third chapter of the thesis. Difficult-to-distinguish from each other species of Quedius s. str. have historically been mixed and their distributions were therefore not properly known. The systematic revision solved this problem too, and prepared the lineage for a more in-depth biogeographical analysis. Subsequently, biogeography is at the core of the fourth chapter which contains a published paper, a manuscript in preparation and a preliminary summary of data towards the third manuscript in a pipeline. The published paper deals with the species of the quediine genus Quedionuchus for which, by using both DNA barcoding and geometric morphometrics, it was possible to establish robust species limits. The paper showed that a commonly known wide-spread trans-Holarcticspecies in this forest-dwelling group confined to subcortical spaces was an artefact of insufficient taxonomy. This conclusion is plausible as there has been no connection of boreal forest between the Eurasian and North American continents since at least 5.3 Ma. The manuscript of the second paper in this chapter uses a more rigorous inference to reconstruct biogeographic history of the revised Holarctic lineage, Quedius s. str. It showed that the subgenus began to spread from the Western Palearctic at the beginning of the Miocene about 20 Ma. In connection with the cooling of our planet over the past 10 million years, several of its current species have emerged. Around 6.4 Ma one lineage of the subgenus migrated from the East Palearctic across Beringia to the North American continent and further diversified there. However, it was not possible to see any species formation in Quedius s. str. in connection with the Quaternary ice ages either in North America or in Eurasia. To shed light on exactly what effect these, most recent climatic fluctuations had, we looked at the genetic structure within populations of one widespread Eurasian species Quedius fuliginosus. Although this part of the dissertation is still not fully completed, the initial results show that there may be two populations of the species that are both widespread across most of the West and Central Palaearctic boreal and temperate regions. Plus, there are at least two other populations isolated in the Caucasus and Middle Asian mountains, respectively. As a final fifth chapter of the thesis, I zoom in to a very local level and present a website that can help gather knowledge about Quediini and all other Danish beetle species, the Danish Beetle Bank (www.billebank.dk). In addition to having images of over half of the known Danish species, I hope that it can become a place that collects and passes on all the knowledge that is at risk of being forgotten, either because it lies with individuals or that it is only found in historical literature not yet digitized.