Distribution and ecology of larval hydropsychidae (Trichoptera) in Newfoundland

Abstract

Hydropsychidae are represented in Newfoundland by only eight species compared to 145 species in North America. It was predicted that these eight widely distributed hydropsychids would differ in their distribution and ecology here because of the reduced species diversity and the broad diversity of lotic habitats available in the glacial-fluvial morphology of Newfoundland streams. Specifically, that Newfoundland species would differ in their physical niche and that water temperature and food resources would influence their distribution. -- Distribution of Newfoundland Hydropsychidae was strongly influenced by lake outlets, which had higher nutrient concentrations and warmer temperatures than downstream sites. All species occurred in forested and barren landscapes. Densities of hydropsychids were elevated at outlets and in forested streams. Parapsyche apicalis was restricted to cooler streams. Stream size also influenced the distribution of some species. Other physical factors did not correlate with densities. The hypothesized reduced spatial and nutritional competition between species because of the impoverished fauna did not translate into an expanded habitat range in Newfoundland. -- A logistic model was derived to provide a basis of comparison for hydropsychid, plankton and periphyton abundances amongst streams of different sizes. Across stream comparisons showed rapid changes near outlets. Abundances of C. pettiti and H. betteni declined rapidly below outlets, H. slossonae had a fairly constant longitudinal abundance and H. sparna increased in abundance downstream. Zooplankton, H. betteni and total hydropsychid abundance showed similar longitudinal trends.