Selection by parasitoid females among closely related hosts based on volatiles: Identifying relevant chemical cues.

Lisa Fors,Laima Blažytė-Čereškienė,Peter A Hambäck,Thomas A Verschut,Raimondas Mozuraitis

doi:10.1002/ece3.3877

Lisa Fors, Laima Blažytė-Čereškienė + Show 3 more

Open Access

https://doi.org/10.1002/ece3.3877

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Abstract

Parasitoid fitness is influenced by the ability to overcome host defense strategies and by the ability of parasitoid females to select high‐quality host individuals. When females are unable to differentiate among hosts, their fitness will decrease with an increasing abundance of resistant hosts. To understand the effect of mixed host populations on female fitness, it is therefore necessary to investigate the ability of female parasitoids to select among hosts. Here, we used behavioral assays, headspace volatile collection, and electrophysiology to study the ability of Asecodes parviclava to use olfactory cues to select between a susceptible host (Galerucella calmariensis) and a resistant host (Galerucella pusilla) from a distance. Our studies show that parasitoid females have the capacity to distinguish the two hosts and that the selection behavior is acquired through experiences during earlier life stages. Further, we identified two volatiles (α‐terpinolene and [E]‐β‐ocimene) which amounts differ between the two plant–herbivore systems and that caused behavioral and electrophysiological responses. The consequence of this selection behavior is that females have the capacity to avoid laying eggs in G. pusilla, where the egg mortality is higher due to much stronger immune responses toward A. parviclava than in larvae of G. calmariensis.

Highlights

Evolution of parasitoids in parasitoid–host interactions depends on their ability to overcome host defense strategies and on the ability of parasitoid females to select the highest quality individuals of either the same or different host species
It is well known that most parasitoids use volatiles, and host-induced volatiles, to locate suitable hosts (Vet & Dicke, 1992), but the volatile profiles may not be sufficiently different to allow parasitoids to differentiate among host species using only olfactory cues
The studies suggesting that different herbivore species emit different volatile profiles when feeding on the same plant are restricted to cases where herbivores are distantly related or do not share parasitoids (De Moraes et al, 1998; de Rijk et al, 2013), mainly allowing parasitoids to differentiate between host and nonhost species

Summary

| INTRODUCTION

Evolution of parasitoids in parasitoid–host interactions depends on their ability to overcome host defense strategies and on the ability of parasitoid females to select the highest quality individuals of either the same or different host species (van Alphen & Drijver, 1982; Desneux, Blahnik, Delebecque, & Heimpel, 2012; Dupas, Dubuffet, Carton, & Poirie, 2009; Rolff, 2002; Rolff & Kraaijeveld, 2001). Preference–performance experiments with parasitoid females generally indicate that female preference is related to offspring performance (Dubuffet, Alvarez, Drezen, Van Alphen, & Poirie, 2006; Dupas et al, 2009), but in some cases, parasitoid females have been found to select hosts where offspring have a very low survival (Heimpel, Neuhauser, & Hoogendoorn, 2003) Because these studies generally do not identify the sensory cues involved, it is unknown if the inability of parasitoid females to select among hosts may be due to a lack of suitable cues. We used electroantennographic detection as a measure of the ability of parasitoid antennae to detect these compounds and compared the responses to a range of other compounds These experiments confirm the result from the behavioral studies, suggesting that A. parviclava females are able to differentiate between the two host species based on volatiles. We identify two compounds that may explain the host selection behavior

| MATERIALS AND METHODS

| DISCUSSION

Findings

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