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

J. H. Cushman, Thomas G Whitham

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Phloem-feeding membracids (Publilia modesta) compete intraspecifically for the protective services of an ant mutualist (Formica altipetens). By experimentally increasing membracid densities, the authors 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 into a 92% decrease in the production of newly eclosed membracid adults. -from Authors

Original languageEnglish (US)
Pages (from-to)851-865
Number of pages15
JournalAmerican Naturalist
Issue number4
StatePublished - 1991
Externally publishedYes


ASJC Scopus subject areas

  • Ecology

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