Herbivore specificity and the chemical basis of plant-plant communication in Baccharis salicifolia (Asteraceae).
It is well known that plant damage by leaf-chewing herbivores can induce resistance in neighbouring plants. It is unknown whether such communication occurs in response to sap-feeding herbivores, whether communication is specific to herbivore identity, and the chemical basis of communication, including specificity. We carried out glasshouse experiments using the California-native shrub Baccharis salicifolia and two ecologically distinct aphid species (one a dietary generalist and the other a specialist) to test for specificity of plant-plant communication and to document the underlying volatile organic compounds (VOCs). We show specificity of plant-plant communication to herbivore identity, as each aphid-damaged plant only induced resistance in neighbours against the same aphid species. The amount and composition of induced VOCs were markedly different between plants attacked by the two aphid species, providing a putative chemical mechanism for this specificity. Furthermore, a synthetic blend of the five major aphid-induced VOCs (ethanone, limonene, methyl salicylate, myrcene, ocimene) triggered resistance in receiving plants of comparable magnitude to aphid damage of neighbours, and the effects of the blend exceeded those of individual compounds. This study significantly advances our understanding of plant-plant communication by demonstrating the importance of sap-feeding herbivores and herbivore identity, as well as the chemical basis for such effects.
Misión Biológica de Galicia (MBG-CSIC), Apdo. 28, Pontevedra, Galicia, 36080, Spain.
Xoaquín
X
Moreira
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA.
Colleen S
CS
Nell
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA.
Angelos
A
Katsanis
Institute of Biology, Laboratory of Functional Ecology, University of Neuchâtel, Rue Emile-Argand 11, Neuchâtel, 2000, Switzerland.
Sergio
S
Rasmann
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA.
Kailen A
KA
Mooney
D000818:Animals; D001042:Aphids / Q000502:physiology; D031175:Baccharis / Q000469:parasitology*; D060434:Herbivory / Q000502:physiology*; D058507:Host Specificity; D055549:Volatile Organic Compounds / Q000378:metabolism
D055549:Volatile Organic Compounds

Aphis gossypii
; 
Uroleucon macolai
; emitters; herbivory; receivers; volatile organic compounds (VOCs)