Contributions towards a better understanding of millipede phylogenetics and sawfly genomics

Abstract

A loss of biodiversity on a scale and rate comparable to the great extinction events, as a result of anthropogenic activity, has been documented for plants, animals, and micro-organisms. In order to foster a sustainable future, it is imperative that we have a well founded understanding and knowledge of biodiversity as well as the factors that generate and sustain it. This thesis presents research from a range of disciplines all aimed at furthering our understanding of arthropod biodiversity with a focus on Diplopoda (millipedes) and Hymenoptera (sawflies, wasps, ants, and bees). After providing a general introduction on biodiversity research and the current state of knowledge on millipedes and hymenopterans in Chapter 1, the four following chapters (Chapter 2 – Chapter 5) detail research on the taxonomy and systematics of a small but understudied order of volvating millipedes, the Glomerida. Within these chapters, I utilize a combination of scanning electron microscopy based morphology, DNA barcoding, mitochondrial genomics, and phylogenomic analyses of transcriptome based datasets to investigate the intraordinal relationships of the Glomerida as well as the relationships between the Glomerida and its two potential sister-groups: the Sphaerotheriida and Glomeridesmida. In Chapter 6, I take advantage of the well resolved relationships of the major hymenopteran groups and our knowledge of the timing of their divergence to directly study the evolutionary mechanisms that enabled the diversification of the group. For this, I, along with a large international team of researchers, compare the genomes of a phytophagous and a parasitoid sawfly to those of wasps, ants, and bees (Apocrita). Based on these comparisons, we present insights into the composition of the ancestral hymenopteran genome, the dynamics of hymenopteran genome evolution, the transition from phytophagy to parasitoidism, and the factors that enabled the tremendous diversification of the Apocrita.