title: Synergistic effects of direct and indirect defences on herbivore egg survival in a wild crucifer.
abstract: Evolutionary theory of plant defences against herbivores predicts a trade-off between direct (anti-herbivore traits) and indirect defences (attraction of carnivores) when carnivore fitness is reduced. Such a trade-off is expected in plant species that kill herbivore eggs by exhibiting a hypersensitive response (HR)-like necrosis, which should then negatively affect carnivores. We used the black mustard (Brassica nigra) to investigate how this potentially lethal direct trait affects preferences and/or performances of specialist cabbage white butterflies (Pieris spp.), and their natural enemies, tiny egg parasitoid wasps (Trichogramma spp.). Both within and between black mustard populations, we observed variation in the expression of Pieris egg-induced HR. Butterfly eggs on plants with HR-like necrosis suffered lower hatching rates and higher parasitism than eggs that did not induce the trait. In addition, Trichogramma wasps were attracted to volatiles of egg-induced plants that also expressed HR, and this attraction depended on the Trichogramma strain used. Consequently, HR did not have a negative effect on egg parasitoid survival. We conclude that even within a system where plants deploy lethal direct defences, such defences may still act with indirect defences in a synergistic manner to reduce herbivore pressure.
authors.affiliation: Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands nina.fatouros@wur.nl.
authors.forename: Nina E
authors.initials: NE
authors.lastname: Fatouros
authors.affiliation: Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Ana
authors.initials: A
authors.lastname: Pineda
authors.affiliation: Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands Dutch Butterfly Conservation, Mennonietenweg 10, 6702 AD Wageningen, The Netherlands.
authors.forename: Martinus E
authors.initials: ME
authors.lastname: Huigens
authors.affiliation: Department of Plant Breeding, Wageningen University and Research Centre, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Colette
authors.initials: C
authors.lastname: Broekgaarden
authors.affiliation: Plant Pathology Department, University of Florida, PO Box 110680, Gainesville, FL, USA.
authors.forename: Methew M
authors.initials: MM
authors.lastname: Shimwela
authors.affiliation: Fundación PROINPA, Avenida Elias Meneces Km 4, El Paso, Cochabamba, Bolivia.
authors.forename: Ilich A
authors.initials: IA
authors.lastname: Figueroa Candia
authors.affiliation: Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Patrick
authors.initials: P
authors.lastname: Verbaarschot
authors.affiliation: Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6708 PB Wageningen, The Netherlands.
authors.forename: Tibor
authors.initials: T
authors.lastname: Bukovinszky
mesh_terms: D000818:Animals; D002080:Butterflies / Q000469:parasitology* / Q000502:physiology*; D052284:Clutch Size; D005819:Genetic Markers; D060434:Herbivory; D009149:Mustard Plant / Q000502:physiology*; D010063:Ovum / Q000469:parasitology; D055549:Volatile Organic Compounds; D014863:Wasps / Q000502:physiology
chemical_list: D005819:Genetic Markers; D055549:Volatile Organic Compounds
keywords: PR1; Pieris rapae; Trichogramma; defence trade-offs; hypersensitive response; oviposition-induced plant volatiles