Knowing your enemies: Integrating molecular and ecological methods to assess the impact of arthropod predators on crop pests

Abstract

The importance of natural enemies as the foundation of integrated pest management (IPM) is widely accepted, but few studies conduct the manipulative field experiments necessary to directly quantify their impact on pest populations in this context. This is particularly true for predators. Studying arthropod predator-prey interactions is inherently difficult: prey items are often completely consumed, individual predator-prey interactions are ephemeral (rendering their detection difficult) and the typically fluid or soft-bodied meals cannot be easily identified visually within predator guts. Serological techniques have long been used in arthropod predator gut-contents analysis, and current enzyme linked immunosorbent assays (ELISA) are highly specific and sensitive. Recently, polymerase chain reaction (PCR) methods for gut-contents analysis have developed rapidly and they now dominate the diagnostic methods used for gut-contents analysis in field-based research. This work has identified trophic linkages within food webs, determined predator diet breadth and preference, demonstrated the importance of cannibalism and intraguild predation within and between certain taxa, and confirmed the benefits (predator persistence) and potential disadvantages (reduced feeding on pest species) of the availability of alternative nonpest prey. Despite considerable efforts to calibrate gut-contents assays, these methods remain qualitative. Available techniques for predator gut-contents analysis can provide rapid, accurate, cost-effective identification of predation events. As such, they perfectly compliment the ecological methods developed to directly assess predator impacts on prey populations but which are imperfect at identifying the key predators. These diagnostic methods for gut-contents analysis are underexploited in agricultural research and they are almost never applied in unison with the critical field experiments to measure predator impact. This paper stresses the need for a combined approach and suggests a framework that would make this possible, so that appropriate natural enemies can be targeted in conservation biological control.

The use of DNA barcodes in food web construction—terrestrial and aquatic ecologists unite!

“…These entries cover the technical challenges and bioinformatics decisions involved in turning from DNA barcoding single individuals to metabarcoding biological communities (Cristescu 2014;Clare et al 2016), the rise of modern molecular dietary analysis (Symondson 2002;Furlong 2015), recommendations for best practices in diet analyses (King et al 2008), and comparisons of specific molecular techniques for reconstructing trophic interactions (Razgour et al 2011;Pompanon et al 2012;Clare 2014;Toju 2015;Evans et al 2016). Rather than repeating what has been said better before, we thus bypass these steps and explicitly focus on a fundamental, conceptual issue: how barcode-based techniques in a broad sense can be applied to improve our understanding of how food webs are actually structured-to resolve both the nodes of the web and the links between them.…”

Barcoding the food chain: from Sanger to high-throughput sequencing

“…DNA barcoding allows researchers to examine trophic interactions within agro-ecosystems (Clare 2014), contributing, for example, to our understanding of how farmland predators regulate pest species (Piñol et al 2014;Furlong 2015). Traditionally, understanding predator-prey interactions required morphological examination of gut contents, faeces, and regurgitated pellets, with poor and taxonomically biased resolution (Sheppard and Harwood 2005).…”

“…One solution is to model occupancy (species-level) or spatial mark-recapture (individual-level) data, although careful experimental designs are needed before data collection can begin (Schnell et al 2015). Finally, barcoding techniques can always be used in parallel with a subsample of traditional trapping methods and morphological analysis of samples (Furlong 2015).…”

MALDI-TOF MS Profiling-Advances in Species Identification of Pests, Parasites, and Vectors

“…Accurate and rapid species identification of pests and parasites is extremely important for initiating species-specific treatment procedures, understanding the epidemiology, monitoring of outbreaks, and designing control measures (Gibson, 2009; Furlong, 2015). Traditionally, trained taxonomists or entomologists visually examine or observe microscopically the morphological characteristics for species determination.…”