Plants release airborne chemicals (volatile organic compounds, VOCs) in response to a variety of abiotic and biotic stimuli, including herbivory by insects. These chemicals are frequently used by insect carnivores as host-finding cues, and may act as a type of indirect defense for plants. Though there is increasing evidence for the ubiquity of these systems, biologists still have not fully evaluated how biotic and abiotic factors interact to affect the overall quality of cues and the ability of insects to interpret noisy signals. Here, we examine how herbivory, temperature, relative humidity, and water availability interact to structure VOC emission in a wild population of Datura wrightii plants in the field and in the lab.
Results/Conclusions
Emission rates and the majority of variation in the composition of blends were structured mainly by variation in abiotic factors, not herbivory. However, a linear discriminant analysis (LDA) showed that it is possible to distinguish between plants attacked by herbivores and those that were not, based on blend composition. These results suggest that cues emitted by plants may be noisy because of variation in key environmental factors, and that LDA and other dimensionality-reducing techniques can be important tools in determining what information insect carnivores are using to find hosts.