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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Population Ecology 2
Population fluctuations in caddisflies inhabiting high-elevation wetlands in central Colorado
S.A. Wissinger1,2. 1Biology Department, Allegheny College, Meadville, PA 16335 USA, 2Rocky Mountain Biological Laboratory, Crested Butte, CO 81224 USA
There are relatively few long-term data on population fluctuations in aquatic insects. In this paper I present 15 years of census data on four species of caddisflies (Trichoptera) that inhabit a remote complex of 50 high-elevation ponds and wetlands. Populations of one of the dominant species, Limnephilus externus crashed in both permanent and temporary habitats when an extraordinarily early snowfall prevented oviposition. In the absence of L. externus, L. picturatus, a congener that oviposits earlier, increased dramatically and expanded its range into ponds where it had been historically absent. Subsequent recovery of L. externus populations was coupled with a decline and habitat contraction of L. picturatus. Fluctuations in the size of the dominant species in temporary habitats, Asynarchus nigriculus, were not coupled with changes in Limnephilus abundance, but were correlated with inter-annual variation in drying date. Fluctuations in a permanent-habitat species, Agrypnia deflata, were not obviously coupled to fluctuations in the other caddisfly species or to the abundance of salamanders, the top predator in permanent ponds. These results emphasize the importance of long-term data for detecting natural population fluctuations, and provide the basis for experimental studies designed to isolate the causes and consequences of such fluctuations.
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