Effects of simulated grazing on different genotypes of Bouteloua gracilis: how important is morphology? |
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Authors: | P M Kotanen J Bergelson |
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Institution: | (1) Department of Ecology and Evolution, The University of Chicago, 1101 East 57th St., Chicago, IL 60637, USA, US |
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Abstract: | Populations of grasses exposed to grazing by vertebrates often exhibit reduced stature, increased tillering, reduced flowering,
and other morphological differences which distinguish them from ungrazed populations. These differences frequently are interpreted
as an adaptive response that reduces grazing damage; however, there are few experimental tests of this hypothesis. This paper
describes a field experiment designed to determine whether morphological variation among genotypes of the grass Bouteloua gracilis is related to variation in their responses to grazing. Eleven genotypes differing in morphological and reproductive characters
were transplanted into a shortgrass steppe community near Fort Collins, Colorado. Replicates of each genotype were subjected
to clipping treatments intended to realistically simulate three grazing intensities. After two growing seasons, different
genotypes still maintained significant differences in a wide range of morphological and demographic characters. However, there
were few significant effects of grazing treatment, and no significant genotype×treatment interactions. These results suggest
that for B. gracilis clipped in simulation of natural grazing, defoliation has few short-term effects on fitness components, and intrapopulation
morphological variation has few consequences for defoliation resistance.
Received: 22 March 1999 / Accepted: 26 October 1999 |
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Keywords: | Bouteloua gracilis Grazing Morphology Resistance Shortgrass steppe Tolerance |
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