Concepts of evolutionary ecology in Nearctic Trichoptera

Abstract

There are 144 genera of Nearctic Trichoptera compared with 60 Ephemeroptera, 82 Odonata, and 87 Plecoptera. Trichoptera have the broadest range in habitat and trophic category; the distribution of genera in the Eastern Deciduous Forest Biome shows a good fit to expected numbers according to a model showing functional aspects of an eastern stream ecosystem.

Filter-feeding Trichoptera partition fine particulate organic resources. In the Hydropsychidae, Arctopsychinae filter large particles in mountain streams; Macronematinae filter small particles in large rivers; Hydropsychinae are generalists but are under-represented in the western montane region. The Polycentropodidae feed mainly on fine particles in the East; the only two genera in the western montane region are predacious. The Philopotamidae feed on tiny particles and are uniformly distributed in the East and West.

One-third of Nearctic Trichoptera genera are Limnephilidae. Apataniinae, Neophylacinae, Goerinae and most Dicosmoecinae are confined to lotic habitats where they graze on rock surfaces. Limnephilinae and Pseudostenophylacinae are shredders, and are more diversified ecologically, especially in lentic habitats including transient waters. In the upstream areas of western montage regions, shredder/collector and grazer genera of limnephilids are equally common; grazers are fewer in the East. The evolution of western Trichoptera appears to have been influenced by food resources available in more open streams in largely coniferous forest.