Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Masayoshi Uefune,Junji Takabayashi,Rika Ozawa,Soichi Kugimiya

doi:10.12688/f1000research.2-57.v2

Masayoshi Uefune, Junji Takabayashi + Show 2 more

Open Access

https://doi.org/10.12688/f1000research.2-57.v2

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Abstract

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and ( Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

Highlights

Plants infested by herbivorous insects release volatiles called herbivoreinduced plant volatiles (HIPVs), which attract carnivorous natural enemies such as parasitic wasps and predators[1,2,3]
Response of cotesia vestalis females to Blend A vs. Blend B We first confirmed that oviposition-inexperienced female wasps showed no significant preference between Blends A and B in the choice chamber (G-test, Gt = 5.9925, P = 0.1997; heterogeneity among samples: Gh = 3.9711, P = 0.2646; pooled effect of treatment: Gp = 2.0213, P = 0.1551) (Figure 1a)
When the female wasps had prior oviposition experience in the presence of Blend B, they showed a significant preference for Blend B over Blend A (Gt = 7.9547, P = 0.0470; Gh = 2.6415, P = 0.2669; Gp = 5.3131, P = 0.0212) (Figure 1c)

Summary

Introduction

Plants infested by herbivorous insects release volatiles called herbivoreinduced plant volatiles (HIPVs), which attract carnivorous natural enemies such as parasitic wasps and predators[1,2,3]. Blends of HIPVs differ from those of volatiles emitted by intact or artificially damaged plants and are specific to plant species, cultivars and developmental stage, as well as to herbivore species and developmental stage[1,2,3]. Natural enemies facilitate this specificity to find their victims. These plant-specific responses by carnivores may be due to innate olfactory preferences or to olfactory learning of prey-infested plant volatiles[4,5,6,7,8,9,10,11,12,13,14,15]

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