Herbivore-induced plant volatiles mediate in-flight host discrimination by parasitoids

• Published in: Journal of chemical ecology Vol. 31; no. 9; pp. 2033 - 2047
• Main Authors: Fatouros, N.E, Loon, J.J.A. van, Hordijk, K.A, Smid, H.M, Dicke, M
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01.09.2005; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; biological control; braconidae; Brassica - metabolism; Brassica - parasitology; brussels-sprouts plants; Butterflies - parasitology; Butterflies - physiology; c-rubecula; cabbage plants; carnivorous arthropods; Chemotactic Factors - analysis; Chemotactic Factors - metabolism; Cotesia glomerata; Cotesia rubecula; damaged plants; Feeding Behavior; Female; Fundamental and applied biological sciences. Psychology; General aspects; Herbivores; host preferences; Host-Parasite Interactions; hymenoptera; infochemical use; insect control; insect pests; Larva - parasitology; Larva - physiology; Mass spectrometry; Odorants - analysis; parasitoids; Pieris rapae; pieris-brassicae; plant damage; Plant Leaves - metabolism; Plant Leaves - parasitology; plant-insect relations; tritrophic interactions; volatile compounds; Wasps - physiology; Volatile compound; Insecta; Flight; Host; Pieris; Tritrophic system; Induced plant defense; Locomotion; Plant; Induced defense; Discrimination; Parasitoid; Cotesia; Entomophagous; Animal plant relation; Arthropoda; tritrophic interactions; Lepidoptera; Pieridae; Headspace; headspace analysis; Invertebrata; Interspecific relation
• ISSN: 0098-0331; 1573-1561
• DOI: 10.1007/s10886-005-6076-5

Herbivore feeding induces plants to emit volatiles that are detectable and reliable cues for foraging parasitoids, which allows them to perform oriented host searching. We investigated whether these plant volatiles play a role in avoiding parasitoid competition by discriminating parasitized from unparasitized hosts in flight. In a wind tunnel set-up, we used mechanically damaged plants treated with regurgitant containing elicitors to simulate and standardize herbivore feeding. The solitary parasitoid Cotesia rubecula discriminated among volatile blends from Brussels sprouts plants treated with regurgitant of unparasitized Pieris rapae or P. brassicae caterpillars over blends emitted by plants treated with regurgitant of parasitized caterpillars. The gregarious Cotesia glomerata discriminated between volatiles induced by regurgitant from parasitized and unparasitized caterpillars of its major host species, P. brassicae. Gas chromatography-mass spectrometry analysis of headspace odors revealed that cabbage plants treated with regurgitant of parasitized P. brassicae caterpillars emitted lower amounts of volatiles than plants treated with unparasitized caterpillars. We demonstrate (1) that parasitoids can detect, in flight, whether their hosts contain competitors, and (2) that plants reduce the production of specific herbivore-induced volatiles after a successful recruitment of their bodyguards. As the induced volatiles bear biosynthetic and ecological costs to plants, downregulation of their production has adaptive value. These findings add a new level of intricacy to plant-parasitoid interactions.