Pascal’s Wager in defending against insect herbivores: Do goldenrod plants bias their use of information away from costly mistakes?

While plants are often perceived as passive members of ecological communities, there is a growing appreciation that plants sense and react to environmental cues in ways that are analogous to animals. We borrowed a theory from animal behavior, risk management theory, and applied it to tall goldenrod (Solidago altissima) and how it uses information to defend against its insect herbivores. We exposed plants to two cues indicating heightened risk of herbivory, putative sex pheromone of a specialist gall-inducing fly (Eurosta solidaginis) or herbivore-induced plant volatiles (HIPV) caused by generalist caterpillar (Helicoverpa zea) feeding, using a full factorial design (exposure to the specialist cue, the generalist cue, both, or none). We then matched or mismatched plants to the herbivores associated with the cues (caterpillars, flies, both, or neither) and recorded leaf damage, gall formation, and flower and rhizome production at the end of the season. Based on risk management theory, we predicted that plants would bias their defense decisions to minimize the most costly (in terms of reproduction) mismatch. We tested three different plant genotypes to test whether different genotypes might have different defense strategies. While we are still analyzing fitness measures, we found that all genotypes increased defenses against caterpillars when exposed to HIPV. Only one genotype was better defended against galling after exposure to the fly pheromone, and another genotype became more susceptible to galling after exposure to HIPV, suggesting that some genotypes might prioritize defenses against one type of damage over another.