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Communication at the NABS Annual meeting, Keystone, 2000
(30) REGIONAL INFLUENCES ON LOCAL COMMUNITY STRUCTURE: ARE
STREAM BENTHIC COMMUNITIES SATURATED?.
D.S. Finn and N.L. Poff. Department of Biology, Colorado State University, Fort Collins, CO 80523
Little is known about the processes controlling stream community structure. An
important question to address in examining this issue is whether local communities are
saturated with species from the regional pool. We approached this problem on a small
scale by comparing local richness on individual stones to regional richness, defined on a
riffle scale. We sampled 5 riffles in each of 4 Rocky Mountain streams across an
altitudinal gradient from 3400 to 2650 m. Riffles were chosen to minimize geomorphic
differences between streams. Within riffles, 15-18 individual stones were sampled
(ranging in size from gravel to boulder) and species-area curves constructed. Most curves
were significant (p<0.05), allowing us to calculate standardized local richness values.
Regional richness was calculated from intensive kicknet samples for each riffle. Results
indicate that local communities are proportionally sampled from the region, with no
evidence for saturation. Interestingly, we also found that community composition at
undisturbed and physically similar sites within an ecoregion can vary dramatically.
These results support the idea that stream communities are relatively noninteractive and
may be structured primarily by spatial and temporal patchiness. An important
implication is that local community structure cannot be explained without reference to the
regional species pool.
Presented at 2:15 PM on Monday, May 29, 2000 in Spatial and Temporal Variation in Aquatic Communities I
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