Interactions between predation risk and plant resistance for Colorado potato beetle behavior, physiology and performance

Background/Question/Methods

The non-consumptive effects of predators, where prey respond to predation risk but are not eaten, are a major component of the total effect of predators on growth and survival of prey and the prey’s resource. This strong impact of NCE’s is perhaps non-intuitive, but occurs because prey have such strong responses to the presence of predators. The non-consumptive effects of predators on prey growth and demography are typically stronger under conditions where the prey’s food availability is low compared to where it is abundant. However, the ecologically important and abundant insect herbivores are not usually limited by the amount of food per se, but are more often limited by the amount of high quality food. In this study, we tested the effect of manipulating predation risk by exposing Colorado potato beetle larvae to predaceous stinkbugs that were surgically manipulated to they could hunt but not kill prey on control potato foliage and on foliage that had been treated with jasmonic acid to induce plant defenses. Predation risk and plant quality manipulations were initiated at hatching until larvae pupated and leaf consumption and larval weight was measured every three days.  Adult longevity, egg production and performance of offspring were also measured.

Results/Conclusions

Beetle growth and consumption were reduced in the predation risk treatment.  There was no independent effect of plant resistance, but the response to predators was stronger on high quality plants compared to plants induced with jasmonic acid. Larval development time was not affected by predation risk or plant resistance alone, but was lengthened when both stresses were present. Assimilation efficiency was lower in the predation risk and plant resistance treatments. Exposure of larvae to predation risk had carry-over effects for their offspring.  In conclusion, plant quality’s main effect was via an interaction with predation risk.  Responses to predation risk were stronger on high quality plants. Extended larval period is a mechanism of compensation for reduced feeding caused by predation risk.  Exposure to predation risk causes changes in prey behavior, development and nutritional physiology.