Money spider dietary choice in pre‐ and post‐harvest cereal crops using metabarcoding

Jordan P Cuff,Jennifer E Stockdale,Ian P Vaughan,Maximillian P.T.G Tercel,Pablo Orozco‐Terwengel,Carsten T Müller,James R Bell,William O.C Symondson,Lorna E Drake

doi:10.1111/een.12957

Abstract

Money spiders (Linyphiidae) are an important component of conservation biological control in cereal crops, but they rely on alternative prey when pests are not abundant, such as between cropping cycles. To optimally benefit from these generalist predators, prey choice dynamics must first be understood. Money spiders and their locally available prey were collected from cereal crops 2 weeks pre‐ and post‐harvest. Spider gut DNA was amplified with two novel metabarcoding primer pairs designed for spider dietary analysis, and sequenced. The combined general and spider‐exclusion primers successfully identified prey from 15 families in the guts of the 46 linyphiid spiders screened, whilst avoiding amplification of Erigone spp. The primers show promise for application to the diets of other spider families such as Agelenidae and Pholcidae. Distinct invertebrate communities were identified pre‐ and post‐harvest, and changes in spider diet and, to a lesser extent, prey choice reflected this. Spiders were found to consume one another more than expected, indicating their propensity towards intraguild predation, but also consumed common pest families. Changes in spider prey choice may redress prey community changes to maintain a consistent dietary intake. Consistent provision of alternative prey via permanent refugia should be considered to sustain effective conservation biocontrol.

Highlights

Effective pest control requires an integrated, augmentative approach, aimed at maximising the effectiveness of natural enemies (Bale et al, 2008; Peterson et al, 2016)
We developed novel polymerase chain reactions (PCRs) primers for the analysis of spider diet using high-throughput sequencing, with a specific focus on the diet of linyphiids
Novel PCR primers were adapted for the exclusion of all spider DNA, with a focus on linyphiids, based upon a primer site slightly 3′ of the general animal barcoding primers LCO1490, and mICOIintR (Leray et al, 2013)

Summary

Introduction

Effective pest control requires an integrated, augmentative approach, aimed at maximising the effectiveness of natural enemies (Bale et al, 2008; Peterson et al, 2016). Spiders are polyphagous generalist predators naturally abundant at densities of 200–600 m−2 in UK crops (Nyffeler & Sunderland, 2003; Shayler, 2005). As a community, they employ a diversity of foraging techniques (Turnbull, 1973; Riechert & Lockley, 1984) which influence food webs via a range of hunting strategies including passive sit-and-wait predation from webs, and active hunting (Michalko & Pekár, 2016). Given that many spiders over-winter in the field, field margins, and hedgerows (Sunderland & Samu, 2000), the post-harvest provision of prey for these predators will influence their abundance and ability to suppress early pest populations in the subsequent crop cycle (Symondson et al, 2002). To understand more precisely how harvest affects spider behavioural dynamics and how to optimise prey availability to support over-wintering and early-season spiders, the prey choice and dietary dynamics of spiders during this period must first be analysed

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Conclusion