Life histories and community structure of the caddisflies (Trichoptera) of two Alaskan subarctic streams

Abstract

The ecology of Trichoptera was studied in two streams in interior Alaska. Monument Creek and West Fork are characterized by cold water temperatures, low allochthonous input and periphyton biomass, and lengthy ice cover. Nine species were found, Rhyacophila vofixa ? (Rhyacophilidae), Glossosoma verdona, G. alascense (Glossosomatidae), Brachycentrus americanus (Brachycentridae), Hydatophylax variabilis, Ecclisomyia conspersa, Onocosmoecus unicolor, Chyranda centralis and Apatania crymophila (Limnephilidae). There were four shredders, three scrapers, one omnivore, and one predator. Within shredders and scrapers, species had sequentially overlapping life histories, perhaps allowing functionally similar species to use the same food resources. Latitudinal gradients in the North American Trichoptera fauna were investigated using approximately 90 studies from the literature and unpublished Alaskan data. Taxonomic richness showed a weak negative correlation with latitude in light trap studies. Hydropsychoidea showed an inverse correlation, while Limnephiloidea and Limnephilidae showed positive correlations with latitude. Density and biomass were also negatively correlated to latitude.