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Orthogonal fitness benefits of nitrogen and ants for nitrogen‐limited plants in the presence of herbivores
Author(s) -
Pringle Elizabeth G.,
Ableson Ian,
Kerber Jennifer,
Vannette Rachel L.,
Tao Leiling
Publication year - 2017
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.2013
Subject(s) - herbivore , aphid , biology , trophic level , honeydew , mutualism (biology) , ecology , nutrient , limiting , aphididae , plant defense against herbivory , ecosystem , botany , homoptera , pest analysis , gene , engineering , mechanical engineering , biochemistry
Abstract Predictable effects of resource availability on plant growth‐defense strategies provide a unifying theme in theories of direct anti‐herbivore defense, but it is less clear how resource availability modulates plant indirect defense. Ant‐plant‐hemipteran interactions produce mutualistic trophic cascades when hemipteran‐tending ants reduce total herbivory, and these interactions are a key component of plant indirect defense in most terrestrial ecosystems. Here we conducted an experiment to test how ant‐plant‐hemipteran interactions depend on nitrogen (N) availability by manipulating the presence of ants and aphids under different N fertilization treatments. Ants increased plant flowering success by decreasing the densities of herbivores, and the effects of ants on folivores were positively related to the density of aphids. Unexpectedly, N fertilization produced no changes in plant N concentrations. Plants grown in higher N grew and flowered more, but aphid honeydew chemistry stayed the same, and neither the density of aphids nor the rate of ant attraction per aphid changed with N addition. The positive effects of ants and N addition on plant fitness were thus independent of one another. We conclude that N was the plant's limiting nutrient and propose that addition of the limiting nutrient is unlikely to alter the strength of mutualistic trophic cascades.