Chemical Ecology of Plant-herbivore Interactions

Plants produce a puzzling diversity of defensive chemicals in their struggle to deter herbivorous enemies. Complex chemical mixtures may present defensive advantages over single compounds, for example via multi-target toxicity or compound-compound facilitation. Chemical diversification is therefore considered a strategy to escape coevolved herbivores. At the same time, such diversification must be costly to the plant, in terms of both raw building blocks and maintenance costs for increasingly complex synthesizing machinery.

We aim to elucidate the selective forces that drive chemical diversification. We use a newly established model plant system and employ a combination of experimental ecology and different techniques including metabolomics, transcriptomics, and phylogenetic comparisons. In a two-pronged approach, we focus on the defensive benefits of diverse chemical mixtures via altered feeding behavior and success of generalist and specialist herbivores, as well as on the cost of diversification in terms of negative impact on plant growth and reproduction. Ultimately, we will thus be able to link variation in genes and metabolites to success in a variable and changing environment.

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• Erysimum cheiranthoides, an ecological research system with potential as a genetic and genomic model for studying cardiac glycoside biosynthesis
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• What doesn't kill you makes you stronger: the burdens and benefits of toxin sequestration in a milkweed aphid
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• Erysimum cheiranthoides, an ecological research system with potential as a genetic and genomic model for studying cardiac glycoside biosynthesis
  T Züst, M Mirzaei, G Jander
  Phytochemistry reviews, 1-13, https://doi.org/10.1007/s11101-018-9562-4 2018
• Population transcriptomic characterization of the genetic and expression variation of a candidate progenitor of Miscanthus energy crops 
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• Trade-offs between plant growth and defense against insect herbivory: an emerging mechanistic synthesis
  T Züst, AA Agrawal
  Annual Review of Plant Biology 68, 513-534, https://doi.org/10.1146/annurev-arplant-042916-040856 2017
• Plant chemical defense indirectly mediates aphid performance via interactions with tending ants 
  Zuest, Tobias; Agrawal, Anurag A. 
  ECOLOGY, 98 (3): 601-607; https://doi.org/10.1002/ecy.1707 MAR 2017
• Population growth and sequestration of plant toxins along a gradient of specialization in four aphid species on the common milkweed Asclepias syriaca 
  Zuest, Tobias; Agrawal, Anurag A. 
  FUNCTIONAL ECOLOGY 30 (4): 547-556 APR 2016 Article (Details)
• Evolution of Plant Growth and Defense in a Continental Introduction 
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• Above-ground herbivory by red milkweed beetles facilitates above- and below-ground conspecific insects and reduces fruit production in common milkweed 
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  JOURNAL OF ECOLOGY 102 (4): 1038-1047 JUL 2014 Article (Details)

• Evolution of cardiac glycosides in Erysimum spp.
• Molecular mechanisms of phytochemical diversification
• Inducible defenses and growth costs
• Herbivore tolerance to basal and novel defenses
• Sequestration of plant toxins and higher-trophic interactions

• Natural variation in the resistance of dandelion (Taraxacum officinale) to aphids
• Physiological mechanisms of toxicity
• Community ecology