The aquatic insect fauna of the Mackenzie River system: Differences among ecoregions and their relation to environmental factors

The Mackenzie River system is the largest and probably most ecologically diverse drainage basin in Canada. It is also subject to increasing natural resource exploitation and the projected effects of climate change in the north, so a detailed knowledge of the invertebrate assemblages across the region is vital for monitoring the effects of these developments on water quality and stream function. We compared aquatic insect assemblages in streams across eight broadly defined ecological regions covering a latitudinal range of approximately 56 to 69 degrees north and attempted to identify ecological and biogeographical factors that affect observed patterns of distribution. In addition to our sampling, data from the Athabasca watershed was contributed by RAMP in northern Alberta. Diversity was negatively correlated with latitude at the ordinal and familial levels of classification, but trends at the generic level were more complex: although most groups were represented by fewer genera as latitude increased, the Chironomidae became increasingly dominant and diverse. Latitudinal patterns were further complicated by unique features of certain regions. For example, streams draining the tundra plains and the Mackenzie Mountains were characterized by lower overall diversity but higher relative abundances of taxa that were rare elsewhere.