Parasitised caterpillars suffer reduced predation: potential implications for intra-guild predation

Wen-bin Chen,Ruo-xue Meng,Geoff M. Gurr,Cheng-xiang Wang,Liette Vasseur,Jian-yu Li,Min-sheng You

doi:10.1038/srep42636

Abstract

Intra-guild predation (IGP) is an important phenomenon structuring ecological communities and affects the success of biological control. Here we show that parasitism by the koinobiont wasp Cotesia vestalis is associated with behavioural changes in its larval host (diamondback moth, Plutella xylostella) that reduce risk of IGP. Compared with unparasitised caterpillars, parasitised P. xylostella moved less frequently to new feeding patches on plants and were less likely to fall from the plant. Wolf spiders killed significantly fewer parasitised larvae. Reflecting their reduced movement and capacity to select plant tissue of optimal quality, parasitised caterpillars fed at a lower rate and exhibited delayed development suggesting a trade-off between IGP avoidance and nutrient intake by the host. This change in behaviour to reduce risk may cascade to the first trophic level and help explain the stability of IGP systems.

Highlights

The overarching aim of this study was to test the hypothesis that the larval foraging behaviour of the globally significant brassica pest, diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), is altered when parasitised by C. vestalis in a manner that reduces the risk of IGP
Subsequent studies explored whether fitness was enhanced in our study system using simulated wind or foraging C. vestalis since both these types of disturbances are faced by P. xylostella in the field; whilst predation was measured in the presence of the wolf spider (Pardosa pseudoannulata Koch (Araneae: Lycosidae)
Reduced movement of parasitised larvae was evident in a separate study using whole plants that extended over three successive days and assessed the numbers of separate leaves fed upon by individual larvae (GLM treatment main effect, F = 6.612, p = 0.013; Fig. 1B)

Summary

Introduction

The overarching aim of this study was to test the hypothesis that the larval foraging behaviour of the globally significant brassica pest, diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), is altered when parasitised by C. vestalis in a manner that reduces the risk of IGP. Subsequent studies explored whether fitness was enhanced in our study system using simulated wind or foraging C. vestalis since both these types of disturbances are faced by P. xylostella in the field; whilst predation was measured in the presence of the wolf spider (Pardosa pseudoannulata Koch (Araneae: Lycosidae). Each of these experiments tested the hypothesis that parasitized larvae were less strongly affected by the respective disturbance factor than were healthy hosts. We tested the hypothesis that reduced movement on the plant by parasitized larvae results in a reduction in nutrient acquisition by parasitised larvae, consistent with a trade-off from the altered feeding behaviour leading to a poorer quality diet

Objectives

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Results