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ASYMMETRIC COMPETITION, HABITAT SELECTION, AND NICHE OVERLAP IN JUVENILE SALMONIDS

ASYMMETRIC COMPETITION, HABITAT SELECTION, AND NICHE OVERLAP IN JUVENILE SALMONIDS 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. Combining a response surface design with different measures of niche overlap reveals how this effect can be both density- and scale-dependent. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecology Ecological Society of America

ASYMMETRIC COMPETITION, HABITAT SELECTION, AND NICHE OVERLAP IN JUVENILE SALMONIDS

Ecology , Volume 85 (1) – Jan 1, 2004

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References (83)

Publisher
Ecological Society of America
Copyright
Copyright © 2004 by the Ecological Society of America
Subject
Regular Article
ISSN
0012-9658
DOI
10.1890/02-0402
Publisher site
See Article on Publisher Site

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. Combining a response surface design with different measures of niche overlap reveals how this effect can be both density- and scale-dependent.

Journal

EcologyEcological Society of America

Published: Jan 1, 2004

Keywords: asymmetric competition ; coho salmon ; habitat selection ; interspecific competition ; isoleg analysis ; niche overlap ; Oncorhynchus kisutch ; Oncorhynchus mykiss ; response surface experimental design ; steelhead trout

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