Abstract
Plant volatiles influence host selection of herbivorous insects. Since volatiles often vary in space and time, herbivores (especially polyphagous ones) may be able to use these compounds as cues to track variation in host plant quality based on their innate abilities and previous experience. We investigated the behavioral response of naïve (fed on artificial diet) and experienced (fed on poplar) gypsy moth (Lymantria dispar) caterpillars, a polyphagous species, towards constitutive and herbivore-induced black poplar (Populus nigra) volatiles at different stages of herbivore attack. In Y-tube olfactometer assays, both naïve and experienced caterpillars were attracted to constitutive volatiles and volatiles released after short-term herbivory (up to 6 hr). Naïve caterpillars also were attracted to volatiles released after longer-term herbivory (24–30 hr), but experienced caterpillars preferred the odor of undamaged foliage. A multivariate statistical analysis comparing the volatile emission of undamaged plants vs. plants after short and longer-term herbivory, suggested various compounds as being responsible for distinguishing between the odors of these plants. Ten compounds were selected for individual testing of caterpillar behavioral responses in a four-arm olfactometer. Naïve caterpillars spent more time in arms containing (Z)-3-hexenol and (Z)-3-hexenyl acetate than in solvent permeated arms, while avoiding benzyl cyanide and salicyl aldehyde. Experienced caterpillars avoided benzyl cyanide and preferred (Z)-3-hexenyl acetate and the homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) over solvent. Only responses to DMNT were significantly different when comparing experienced and naïve caterpillars. The results show that gypsy moth caterpillars display an innate behavioral response towards constitutive and herbivore-induced plant volatiles, but also that larval behavior is plastic and can be modulated by previous feeding experience.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-016-0698-7) contains supplementary material, which is available to authorized users.
Highlights
Plant-derived cues play a role in host-plant selection by herbivorous insects and influence behaviors crucial to insect fitness and survival, such as feeding, mating, and oviposition (Bruce et al 2005; Carrasco et al 2015)
The aim of this study was to investigate the effect of experience on the behavioral responses of polyphagous Lymantria dispar caterpillars to both constitutive and herbivore-induced volatiles emitted by black poplar (Populus nigra), and the potential role of individual volatile compounds as cues for foraging larvae
The results show that naïve early instars of gypsy moth are attracted by volatiles released from conspecific larvae and from undamaged and herbivore-damaged black poplar leaves
Summary
Plant-derived cues play a role in host-plant selection by herbivorous insects and influence behaviors crucial to insect fitness and survival, such as feeding, mating, and oviposition (Bruce et al 2005; Carrasco et al 2015). J Chem Ecol (2016) 42:382–393 correlation between oviposition preference and larval performance in oligophagous species, while this was not the case for polyphagous species (Gripenberg et al 2010). These findings suggest that the larvae of polyphagous insects must be under high selective pressure to make their own host choices. Variation in plant availability may affect competition for shelter and resources as well as predation pressure (Dixon 1970, 1975; Dixon et al 1993; Feeny 1970; Singer et al 2004) All these factors might force larvae to move from one feeding site to another several times during the life cycle
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