Plant chemical defense indirectly mediates aphid performance via interactions with tending ants

Züst, Tobias; Agrawal, Anurag A. (2017). Plant chemical defense indirectly mediates aphid performance via interactions with tending ants. Ecology, 98(3), pp. 601-607. Ecological Society of America 10.1002/ecy.1707

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The benefits of mutualistic interactions are often highly context dependent. We studied the interaction between the milkweed aphid Aphis asclepiadis and a tending ant, Formica podzolica. While this interaction is generally considered beneficial, variation in plant genotype may alter it from mutualistic to antagonistic. Here we link the shift in strength and relative benefit of the ant-aphid interaction to plant genotypic variation in the production of cardenolides, a class of toxic defensive chemicals. In a field experiment with highly variable genotypes of the common milkweed (Asclepias syriaca), we show that plant cardenolides, especially polar forms, are ingested and excreted by the aphid proportionally to plant concentrations without directly affecting aphid performance. Ants consume honeydew, and aphids that excreted high amounts of cardenolides received fewer ant visits, in turn reducing aphid survival. On at least some plant genotypes, aphid numbers per plant were reduced in the presence of ants to levels lower than in corresponding ant-exclusion treatments, suggesting antagonistic ant behavior. While cardenolides thus appear ineffective as direct plant defenses against aphids, the multi-trophic context reveals an ant-mediated negative indirect effect on aphid performance and population dynamics.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Biotic Interactions
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Plant Ecology
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)

UniBE Contributor:

Züst, Tobias

Subjects:

500 Science > 580 Plants (Botany)

ISSN:

0012-9658

Publisher:

Ecological Society of America

Language:

English

Submitter:

Peter Alfred von Ballmoos-Haas

Date Deposited:

05 Apr 2017 15:06

Last Modified:

05 Apr 2017 15:06

Publisher DOI:

10.1002/ecy.1707

PubMed ID:

28060424

Uncontrolled Keywords:

Asclepias syriaca, cardenolides, multitrophic interactions, mutualism

BORIS DOI:

10.7892/boris.95141

URI:

https://boris.unibe.ch/id/eprint/95141

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