Plants eavesdrop on cues produced by snails and induce costly defenses that affect insect herbivores
Although induced defenses are widespread in plants, the degree to which plants respond to herbivore kairomones (incidental chemicals that herbivores produce independent of herbivory), the costs and benefits of responding to cues of herbivory risk, and the ecological consequences of induced defenses remain unclear. We demonstrate that undamaged tomatoes, Solanum lycopersicum, induce defenses in response to a kairomone (locomotion mucus) of snail herbivores (Helix aspersa). Induced defense had significant costs and benefits for plants: plants exposed to snail mucus or a standard defense elicitor (methyl jasmonate, MeJA) exhibited slower growth, but also experienced less herbivory by an insect herbivore (Spodoptera exigua). We also find that kairomones from molluscan herbivores lead to deleterious effects on insect herbivores mediated through changes in plant defense, i.e., mucus-induced defenses of Solanum lycopersicum-reduced growth of S. exigua. These results suggest that incidental cues of widespread generalist herbivores might be a mechanism creating variation in plant growth, plant defense, and biotic interactions.
KeywordsCue Herbivory Indirect effects Induced defenses Kairomone Plant defense
Jessica Casper provided outstanding assistance with herbivory trials; the Damschen lab kindly provided their microbalance. This study was supported by the UW Graduate School Fall Competition Grant to JO and SG and NSF Grant MCB-1329723 to SG and WC. JO was supported by the Vilas Fellowship during a portion of this work. The Biology Department at Virginia Commonwealth University hosted JO while working on this manuscript.
Author contribution statement
JO conceived the study; JO, BC, and SG designed the study; BC, PG, WC, and SS collected the data; and JO analyzed the data and drafted the manuscript; all authors contributed to revising the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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