When does it pay off to prime for defense? A modeling analysis.

Jacob C Douma,Peter J Vermeulen,Niels P R Anten,Marcel Dicke,Erik H Poelman

doi:10.1111/nph.14771

Abstract

Summary Plants can prepare for future herbivore attack through a process called priming. Primed plants respond more strongly and/or faster to insect attack succeeding the priming event than nonprimed plants, while the energetic costs of priming are relatively low.To better understand the evolution of priming, we developed a simulation model, partly parameterized for Brassica nigra plants, to explore how the fitness benefits of priming change when plants are grown in different biotic environments.Model simulations showed that herbivore dynamics (arrival probability, arrival time, and feeding rate) affect the optimal duration, the optimal investment and the fitness benefits of priming. Competition for light increases the indirect costs of priming, but may also result in a larger payoff when the nonprimed plant experiences substantial leaf losses.This modeling approach identified some important knowledge gaps: herbivore arrival rates on individual plants are rarely reported but they shape the optimal duration of priming, and it would pay off if the likelihood, severity and timing of the attack could be discerned from the priming cue, but it is unknown if plants can do so. In addition, the model generated some testable predictions, for example that the sensitivity to the priming cue decreases with plant age.

Highlights

Plants can prepare for future herbivore attack through a process called priming (Frost et al, 2007; Heil & Silva Bueno, 2007; Rodriguez-Saona et al, 2009; Kim & Felton, 2013)
Primed plants have been shown to exhibit faster and/or stronger responses to herbivore attack compared with plants that do not prime, and priming can lead to decreased caterpillar growth rates (Peng et al, 2011), increased pathogen resistance and possibly increased movement of insect herbivores to more palatable plants (Morrell & Kessler, 2016)
We investigated how the optimal investment in priming varies across the range of ecological conditions specified in the previous paragraph

Summary

Introduction

Plants can prepare for future herbivore attack through a process called priming (Frost et al, 2007; Heil & Silva Bueno, 2007; Rodriguez-Saona et al, 2009; Kim & Felton, 2013). Primed plants have been shown to exhibit faster and/or stronger responses to herbivore attack compared with plants that do not prime, and priming can lead to decreased caterpillar growth rates (Peng et al, 2011), increased pathogen resistance (van Hulten et al, 2006; Walters et al, 2008) and possibly increased movement of insect herbivores to more palatable plants (Morrell & Kessler, 2016). Priming is hypothesized to be beneficial for a plant as it may lead to a faster response to the upcoming attack (hereafter called the trigger event), while its costs are estimated to be relatively low compared with immediate defense (Bruce et al, 2007; Frost et al, 2008). Help the plant to prepare for future events while economizing on resources (van Hulten et al, 2006; Frost et al, 2007, 2008; van Hulten et al, 2006)

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Conclusion