Caddisflies of the Yukon - Department of Biological Sciences ...

Caddisflies of the Yukon 791
imposed by these conditions is available from a number of groups; but for aquatic insects
other than Chironomidae (e.g. Oliver 1968) there is little evidence or synthesis. To what
extent did longer colder winters, shorter summers, and shorter photoperiods influence the
success of a group of insects with wholly aquatic larvae? Trichoptera are especially
appropriate for seeking answers to questions of this kind because of their relatively high
diversification; apart from Chironomidae, there are more species of Trichoptera than of any
other group of freshwater insects, and those species occupy an exceptionally wide range of
aquatic habitats and ecological niches (Wiggins and Mackay 1978).
Combining both biogeographic and ecological viewpoints, investigation of the Yukon
Trichoptera reveals results in nature when related species of Nearctic and Palaearctic origins
come together to form aquatic communities. As an ecological testing ground for these natural
experiments, the Yukon is well suited because of its high diversity of aquatic habitats.
Mountain ranges divide the land into several major drainage systems, giving rise to small
rapid streams, which in turn unite to form river systems of increasing order and potential
biological diversity. Marshes, ponds, and lakes abound, providing rich resources for aquatic
insects adapted for life in lentic waters. The treeline, southern margin of the arctic biome,
passes through the northern Yukon at about latitude 67°N. To the north, arctic tundra extends
to the Arctic Ocean; on the slopes of the mountains, biotic zones range through coniferous
forests to alpine tundra and ice-fields. Although freshwater habitats are highly diverse within
the Yukon, the success of insects in forming aquatic communities under climatic conditions
of high latitudes is not well understood. Therefore, examination of these fundamental
biological issues can add to our understanding of the biology of Trichoptera; the same issues
underlie management of aquatic systems in the Yukon Territory.
The analysis begins, necessarily, with a survey of the species of Trichoptera known to
occur in the Yukon. Systematic interpretation of the species has been aided by the advanced
state of knowledge on the Trichoptera of Russia (e.g. Lepneva 1964, 1966; Martynov 1924a),
and by the recent synthesis of aquatic insects of the Russian Far East by I.M. Levanidova
(1982).
Materials and Methods
Most of the collections of Trichoptera studied were made by field parties from the
Department of Entomology, Royal Ontario Museum (ROME), over a 4-year period
from 1979 to 1982, and are deposited there. Collections from other institutions were also
studied: Canadian National Collection of Insects, Ottawa (CNCI); Illinois Natural History
Survey, Champaign, Illinois (INHS); Royal British Columbia Museum (BCPM);
U.S. National Museum of Natural History (USNM); University of British Columbia Insect
Collection, Vancouver (SMDV); Zoological Institute, Russian Academy of Sciences,
St. Petersburg (ZMAS).
All species known from the Yukon Territory are listed, including species recorded in
the scientific literature but not represented in the material we examined—principally records
compiled by Nimmo and Wickstrom 1984 (henceforth NW 1984). Although we have many
larval collections, these records are included only if larvae are the single source of evidence,
as for Allomyia, or can be identified reliably to species as in some Hydropsyche. Distributional
records are grouped by ecogeographic regions of the Yukon (Fig. 1); the detailed list
of our records is too long for inclusion here, but is deposited in the library of the Royal
Ontario Museum. At this early stage in understanding the distribution of Trichoptera in the
Yukon, the records are highly correlated with the access roads; however, some general
patterns seem to emerge. Biological and distributional characteristics of the higher taxa are