| Summary: | This thesis explores the ecological and evolutionary dynamics shaping northern Canadian Diptera assemblages. Despite their significance in Arctic ecosystems, research on northern flies is limited due to taxonomic challenges. Molecular tools, such as the cytochrome c oxidase subunit I (COI) universal animal barcode fragment and Barcode Index Numbers (BINs), provide a solution for studying fly community structure. Real Diptera BIN datasets were used in this thesis to explore fly community assembly. Understanding why groups of species are found at one location but not another requires consideration of their physiological requirements/limitations, dynamics with other species and abiotic environment, and evolutionary history. These processes act as successive sieves at the regional and local scale: evolutionary and biogeographic processes create the species pool; dispersal and physiological tolerances decide species presence; biotic and abiotic interactions operate at individual and species levels. Two popular metrics used to measure “community assembly” are the standard effect size of mean nearest taxon distance (ses.MNTD) and mean pairwise distance (ses.MPD), which compare local samples to the regional species pool. The first study assesses the reliability of calculating ses.MNTD and ses.MPD while subsampling a Diptera dataset from Churchill, Manitoba. Results suggest high sample percentages are necessary for accurate calculations, with optimal subsampling strategies depending on goals. The second study had a continental focus and investigates muscid fly ecology and phylogenetic structure across ecoclimatic zones in the Canadian North using 15,675 Muscidae individuals across 207 BINs. Unique patterns in assemblage composition and evolutionary structure were revealed, highlighting the influence of environmental factors on regional species pools. The third study had a local focus and examined the ecological and evolutionary dynamics of brachyceran Diptera in Churchill, Manitoba. 1,066 Brachycera individuals were ...
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