Phenology and temporal species turnover in an arctic Diptera assemblage

Although Diptera are abundant and ecologically diverse in the Arctic, there has been little research on diversity and phenology of northern flies. Our objective was to document patterns of Diptera diversity and seasonal activity at an Arctic site in Canada. We assessed whether the Diptera assemblage showed successive peaks of activity by different species or whether most species were active throughout the summer. Diptera were collected at Kugluktuk, Nunavut, using Malaise traps through most of the active summer season (late June to mid-August). Higher Diptera were identified to genus or species. Weekly diversity patterns were assessed for taxonomic and trophic groups. Analyses were based on 4608 specimens (123 taxa). Abundance was unimodal with a peak (53% of all specimens) in early July. Overall species richness was almost uniform from 03 July – 10 August, with 14-16% of the total number of species collected in each week. NMDS ordination of overall diversity indicated that weekly species turnover was high, despite the uniform overall richness. Distribution of predators, phytophages and saprophages was comparable to taxonomic patterns, although the early peak in abundance was largely driven by predators. In contrast, the distribution of abundance in a temperate peatland data set (146 species) was more evenly distributed, but unimodal, and there was a more pronounced mid-season peak in species richness. Our results suggest that, in a truncated arctic summer, successive activity periods by different species are maintained, although on shorter time scales than in temperate systems, despite uniform overall species richness through the season.