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.

• Population transcriptomic characterization of the genetic and expression variation of a candidate progenitor of Miscanthus energy crops 
  Juan Yan, Zhihong Song, Qin Xu, Lifang Kang, Caiyun Zhu, Shilai Xing, Wei Liu, Josef Greimler, Tobias Züst, Jianqiang Li, Tao Sang
  MOLECULAR ECOLOGY, 26 (21): 5911-5922; https://doi.org/10.1111/mec.14338 NOV 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
• Title: Population growth and sequestration of plant toxins along a gradient of specialization in four aphid species on the common milkweed Asclepias syriaca 
  Author(s): Zuest, Tobias; Agrawal, Anurag A. 
  Source: FUNCTIONAL ECOLOGY 30 (4): 547-556 APR 2016 
  Document Type: Article (Details)
• Title: Evolution of Plant Growth and Defense in a Continental Introduction 
  Author(s): Agrawal, Anurag A.; Hastings, Amy P.; Bradburd, Gideon S.; et al. 
  Source: AMERICAN NATURALIST 186 (1): E1-E15 Published: JUL 2015 
  Document Type: Article (Details)
• Title: Above-ground herbivory by red milkweed beetles facilitates above- and below-ground conspecific insects and reduces fruit production in common milkweed 
  Author(s): Erwin, Alexis C.; Zuest, Tobias; Ali, Jared G.; et al. 
  Source: JOURNAL OF ECOLOGY 102 (4): 1038-1047 JUL 2014 
  Document Type: Article (Details)

Research topics

• 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

Interdisciplinary

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