Herbivore-Induced Specificity and Diversity in Piper arboreum Volatiles

The essential oils obtained by steam distillation of leaves of Piper species have found several applications in bioeconomy due to their various biological properties. Nevertheless, the analysis of essential oils does not provide information regarding the ecologically relevant volatile organic compounds (VOCs) emitted by metabolically active leaves under real-world conditions, challenged or not by herbivore damage. In this study, P. arboreum growing in a highly diverse area was observed as the host of two generalist caterpillars-Gonodonta maria (Erebidae) and Dysodia spissicornis (Thyrididae)-and one Piper-specialist from the genus Eois (Geometridae). The effect of the leaf attack caused by the three different caterpillars on VOCs emission indicated significant and herbivore-specific changes in leaf-induced responses. The profiles of undamaged leaves showed that the two generalist herbivores induced a higher number of single VOCs and of total VOCs emissions by P. arboreum when compared to the herbivory of the specialist caterpillar. Many of the VOCs emitted by herbivore-damaged leaves contained terpenoids that have been previously shown to attract parasitoids, such as (E)-β-ocimene, linalool, DMNT and (E)-β-caryophyllene. All three herbivores significantly altered the VOC profile of P. arboreum leaves compared to undamaged controls, but specific composition signatures were observed, highlighting the complexity of chemical communication at multitrophic levels.