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- Title
ASYMMETRIC COMPETITION, HABITAT SELECTION, AND NICHE OVERLAP IN JUVENILE SALMONIDS.
- Authors
Young, Kyle A.
- Abstract
The relationship among asymmetric competition, habitat selection, and niche overlap is poorly understood. I conducted a response surface design experiment in artificial stream channels using juvenile coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss) to explore the density- and scale-dependent relationship among asymmetric competition, habitat selection, and niche overlap. In these sympatric populations, juvenile coho are larger, occupy mutually preferred deep, low-velocity pools, and displace steelhead into shallow, high-velocity riffles. I measured habitat selection over a wide range of species' densities under two competitive scenarios: coho larger than steelhead (natural size asymmetry), and species size matched (natural size asymmetry removed). When coho had their natural size advantage, interspecific competition was strongly asymmetric, and habitat selection by both species depended primarily on coho density. Removing the size advantage of coho reduced by half the per capita effect of coho on steelhead habitat selection, which was then affected similarly by intra- and interspecific competition. However, habitat selection by coho still depended more on intra- than interspecific competition. The effect of asymmetric competition on niche overlap was density- and scale-dependent. Asymmetric competition reduced niche overlap nonsignificantly across all densities at the habitat type scale (pools, riffles). At the microhabitat scale (velocity, distance, depth), asymmetric competition reduced niche overlap at low, but not high, densities. Because I manipulated the competitive asymmetry in a single sympatric species pair, this experiment alters a competitive interaction while controlling for evolutionary history and thus provides a direct test of the effect of asymmetric competition on habitat selection and niche overlap.
- Subjects
ASYMMETRIC synthesis; COMPETITION (Biology); HABITAT selection; ECOLOGICAL niche; BIOTIC communities; RESOURCE partitioning (Ecology)
- Publication
Ecology, 2004, Vol 85, Issue 1, p134
- ISSN
0012-9658
- Publication type
Report
- DOI
10.1890/02-0402