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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology I
COLONIZATION DYNAMICS OF MACROINVERTEBRATES IN ALPINE STREAMS AND LAKE OUTLETS.
M. Hieber, C.T. Robinson, U. Uehlinger, and J.V. Ward. Department of Limnology, EAWAG/ETH, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland
Colonization is an important ecosystem process for community maintenance, however, little information exists on colonization patterns in high-elevation streams. We examined the colonization dynamics of habitat patches (i.e., cages filled with natural substrate) by benthic invertebrates in different alpine streams and lake outlets. Streams with a glacial influence, as well as the presence of a preceding lake, had reduced taxon richness relative to rhithral streams. Regardless, colonization was rapid at all sites, showing no significant increases in density or taxon richness after only eight days. High taxa turnover among sampling dates, and a low proportion of taxa present in the cages, suggested that community assembly was in nonequilibrium even after 30 days, i.e., assemblages were in a continuous state of redistribution. The low density and richness of drifting invertebrates further suggested that colonization of patches primarily resulted from invertebrate crawling. Multiple regression analysis indicated that the density of colonists was influenced primarily by small-scale characteristics such as food availability, whereas diversity of colonists was structured primarily by local stream characteristics such as differences in discharge regime. Our results showed that invertebrates rapidly colonize habitat patches in alpine streams primarily by active movement, however, colonization patterns differed among alpine stream types.
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