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Project C02

Principal Investigator: Prof. Dr. Ian T. Baldwin

Are Plant Defenses Chemicals Commonly Sequestered and Metabolized by their Herbivores to Function as Infochemicals in Higher Trophic Level Interactions in Nature?

All plants contain potent chemical defenses: metabolites that prevent the attack of unadapted herbivores, and thwart the growth of adapted herbivores. To cope, herbivores sequester, metabolize, or excrete the defensive metabolites consumed in their food. We propose that this processing of plant defensive metabolites by herbivores produces a vast and largely unexplored collection of chemicals, which provide information about feeding herbivores to their predators, parasitoids, and conspecifics (infochemicals). Furthermore, we contend that a network of infochemicals links plant secondary metabolites to higher trophic levels and sculpts most higher trophic interactions. Uncovering this infochemical network is the goal of this proposal, and it is a goal that we can attain, because we finally have the tools to do so in a rigorous experimental manner under real-world conditions.

The few published examples of infochemicals derived from plant secondary metabolites involve herbivores which are aposematic, having conspicuous warning markings. For aposematic herbivores, infochemicals commonly are plant toxins sequestered by herbivores to protect themselves from their predators, and this co-option of plant defenses is signaled by the herbivore’s aposematic coloration. However, most herbivores are cryptic, camouflaging themselves through their coloration and behavior. Cryptic herbivores must also cope with a vast array of plant secondary metabolites, which frequently involves processing these metabolites into infochemicals. While crypsis limits the number of enemies to those which can locate hidden herbivores, infochemicals derived from host plant toxins may serve as a second barrier to ward off the successful hunters. In our group, we recently discovered that cryptic Manduca sexta larvae can volatilize nicotine from their food plant, Nicotiana attenuata, as an infochemical to deter predation by wolf spiders.

(A) Examples of genes, metabolites, and infochemicals manipulated in plants and herbivores. (B) Schematic representing possible responses of different predators to plant metabolites and herbivore infochemicals, when the herbivore M. sexta recruits unmodified (green) or modified (red) plant metabolites as infochemicals.

Here we propose to ask: 1) what are the hidden infochemical networks that originate from the metabolism of plant defense metabolites by cryptic insects? 2) Do cryptic insects lose their ability to defend against their natural enemies in the absence of plant defense compounds? 3) Do insect herbivores process plant defense metabolites to recruit them against their natural enemies? And 4) can insect herbivores modulate their predator communities by using host plant’s “defense” metabolites as infochemicals? The infrastructure and common goals of the CRC will provide ideal support to ensure the success of this project, as it will require a substantial amount of metabolite characterization, and development of sophisticated metabolite dispensing techniques sufficiently robust to work in the rough and tumble of nature.

Team C02

Prof. Dr. Ian T. Baldwin


Department for Chemical Ecology

Max Planck Institute for Chemical Ecology

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Dr. Meredith Schuman


Department for Chemical Ecology

Max Planck Institute for Chemical Ecology

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Dr. Dapeng Li


Department for Chemical Ecology

Max Planck Institute for Chemical Ecology

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