Competition mediating the outcome of a mutualism: Protective services of ants as a limiting resource for membracids

Cushman, J. Hall and Whitham, Thomas G. (1991) Competition mediating the outcome of a mutualism: Protective services of ants as a limiting resource for membracids. American Naturalist, 138 (4). pp. 851-865. ISSN 0003-0147

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Abstract

Although competition for mutualists is known to be an influential force in plant-animal interactions, its importance in animal-animal associations is largely unexplored. Here, we demonstrate the phloem-feeding membracids (Publilia modesta) compete intraspecifically for the protective services of an ant mutualist (Formica altipetens). By experimentally increasing membracid densities in the field, we observed three negative effects due to competition for ants (1) a 45%-59% reduction in the number of ants tending membracid aggregations, (2) a 63% increase in the abundance of a predatory salticid spider (Pellenes sp.), and (3) a 59% reduction in the mean number of membracid nymphs per plant. In total, the loss of protective services due to competition for mutualists translated in to a 92% decrease in the production of newly enclosed membracid adults. These findings provide the first experimental demonstration that animal species compete for mutualists. In addition, our work indicates that mutualisms can be strongly influenced by the logic biotic neighborhoods in which they occur and thus may be far more variable than previously thought.

Item Type:	Article
Publisher’s Statement:	Copyright 1991 by The University of Chicago.
ID number or DOI:	10.1086/285256
Keywords:	mutualists, competition, mutualism, membracids, ants,
Subjects:	Q Science > QL Zoology
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > Biological Sciences
Date Deposited:	01 May 2017 20:41
URI:	http://openknowledge.nau.edu/id/eprint/2638

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