An effective molecular approach for assessing cereal aphid-parasitoid-endosymbiont networks

Michael Traugott,Zhengpei Ye,Zeljko Tomanovic,Corinna Wallinger,Susanne Girtler,Ines M. G. Vollhardt

doi:10.1038/s41598-017-02226-w

Michael Traugott, Zhengpei Ye + Show 4 more

Open Access

https://doi.org/10.1038/s41598-017-02226-w

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Abstract

Molecular approaches are increasingly being used to analyse host-parasitoid food webs as they overcome several hurdles inherent to conventional approaches. However, such studies have focused primarily on the detection and identification of aphids and their aphidiid primary parasitoids, largely ignoring primary parasitoid-hyperparasitoid interactions or limiting these to a few common species within a small geographical area. Furthermore, the detection of bacterial secondary endosymbionts has not been considered in such assays despite the fact that endosymbionts may alter aphid-parasitoid interactions, as they can confer protection against parasitoids. Here we present a novel two-step multiplex PCR (MP-PCR) protocol to assess cereal aphid-primary parasitoid-hyperparasitoid-endosymbiont interactions. The first step of the assay allows detection of parasitoid DNA at a general level (24 primary and 16 hyperparasitoid species) as well as the species-specific detection of endosymbionts (3 species) and cereal aphids (3 species). The second step of the MP-PCR assay targets seven primary and six hyperparasitoid species that commonly occur in Central Europe. Additional parasitoid species not covered by the second-step of the assay can be identified via sequencing 16S rRNA amplicons generated in the first step of the assay. The approach presented here provides an efficient, highly sensitive, and cost-effective (~consumable costs of 1.3 € per sample) tool for assessing cereal aphid-parasitoid-endosymbiont interactions.

Highlights

Host-parasitoid food webs are among the most studied terrestrial feeding networks and they have been investigated as models to address important questions in network ecology: for example, these networks have been investigated to better understand robustness and restoration of ecological networks[1], apparent competition[2, 3], bottom-up effects on food web structure[4] as well as effects of habitat modification[5], the role of evolutionary processes on food webs[6] and host specificity[7, 8]
The occurrence of bacterial endosymbionts in cereal aphids has been reported in the literature: H. defensa and R. insecticola have been found in S. avenae and Metopolophium dirhodum; and to date, the occurrence of facultative endosymbionts in
With the 18S MP-PCR assay (18SMP) assay, a 196 ± 4 bp (193, 203 bp) 18S fragment was amplified from all the 31 primary parasitoid and 16 hyperparasitoid species examined in this study

Summary

Introduction

DNA-based approaches have been shown to overcome these limitations as they allow the identification of species-specific links between primary parasitoids and hyperparasitoids[29,30,31] and can detect and identify the presence of specific facultative endosymbionts[25, 32]. There is currently no molecular system which allows for the simultaneous detection and identification of aphid, primary parasitoid, hyperparasitoid, and facultative endosymbiont DNA Such a tool is critical for the examination of aphid-parasitoid-endosymbiont networks under field conditions[26, 37], and an improved understanding of these networks may have implications for integrated pest management strategies for aphids. To evaluate the utility of this approach, experiments to determine the sensitivity and specificity of the assay were conducted, and field-collected aphid samples were screened

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Conclusion