Charting biodiversity Scuttle flies and other poorly known insects in Sweden

Sammanfattning: Biodiversity has fascinated people in all times. We as a species are part of the global ecosystem and our survival depends on many other species around us. Charting biodiversity, however, has proven more difficult than one could imagine. When Linnaeus and others started describing which species there are on Earth, people in general, and taxonomists in particular, could not imagine that we would not be finished 300 years later and even less that we would not be able to tell exactly how much there is left to describe.In this PhD thesis, I deal with relatively large organisms (compared to the average size of organisms left to be described), namely insects in general and scuttle flies in particular, within a limited and well-studied geographic region (Sweden). Nevertheless, the results show that we are far from completing the inventory for even this limited portion of global biodiversity. Since it was in Sweden that Linnaeus started his work and where he did most of it, the Swedish flora and fauna belong to the best known in the world. In spite of this, we show in paper I of this thesis that it is likely that a considerable portion of the Swedish insect fauna remains to be discovered. The white spots on the biodiversity map primarily concern small Diptera and Hymenoptera species that are decomposers or parasitoids. The scuttle flies (Diptera: Phoridae) are one of the insect families that contain more undescribed species than species known to science, both in Sweden and elsewhere. The situation is complicated by the fact that a large portion of the known scuttle-fly diversity is placed within a single genus, Megaselia, one of the most species-rich genera in the animal kingdom; almost 40 % of described phorids belong to this genus. Our lack of understanding of phylogenetic relationships within Megaselia has made taxonomic progress on the genus very difficult. In paper II, we define a new natural clade within Megaselia, the lucifrons group, based on both molecular and morphological evidence. We show that the group comprises at least three species in Sweden, one of which is described by us as new to science. In paper III, we present the first comprehensive molecular phylogeny of Megaselia. We identify 22 well-supported natural clades within the genus, comprising at least two species each. These clades are recognized as species groups; most of them have not been described previously. We identify eight additional, isolated single-species lineages, which may turn out to represent multi-species clades when molecular data become available for more species. The paper includes the description of 45 species new to science, all from Sweden. In paper IV, we revise the most basal of the 22 species groups, the spinigera group, and describe one additional new species to science from Sweden in this group. The thesis provides the first reasonably complete phylogenetic framework for Megaselia and its closest relatives, greatly facilitating further research into scuttle-fly diversity in Sweden and elsewhere.