Novel approaches to detecting ecological interactions involving beneficial invertebrates

Hoverflies are beneficial insects in agricultural landscapes: they are important pollinators of flowering plants, including crops, whilst their larvae are natural enemies of plant pests. Hoverflies are also important prey for predators, such as birds, spiders and wasps, which are themselves beneficial species. Additionally, hoverflies display visual mimicry of bees and wasps, which probably evolved because it fools predators into thinking that harmless prey are defended. Hence, predator-prey interactions probably influence hoverfly effectiveness in pollination and pest control, and the adaptive evolution of mimicry. Unfortunately, these interactions are poorly understood: we don't know which species are important predators of hoverflies, or whether hoverflies form a large part of the diet of other beneficial species. This project will combine genetics and immunology to quantify interactions between hoverflies, their predators and prey.
Genetic techniques provide new opportunities to quantify predator-prey interactions via diet analysis. We will screen predators for evidence of hoverfly consumption, and characterise the position of hoverflies in food-webs associated with arable fields, testing for antagonistic interactions between natural enemies of crop pests, and assessing the importance of crop-associated prey in bird diets in agricultural and woodland habitats. Bird faeces will be collected from woodland a) adjacent to and b) distant from arable fields in Nottinghamshire and North Wales. Wasps, hoverfly larvae and spiders will be collected by sweep-netting, hand-searching and trapping in field margins and crops, on farms with and without wildflower margins deployed as part of agri-environment schemes. The student will use hoverfly- and crop-pest-specific PCR/qPCR assays to analyse the occurrence/quantity of hoverfly and pest DNA in faeces/guts from a range of predators, including birds, social wasps (Vespula spp.) and spiders.
Metabarcoding of predator gut contents will be used to further characterise the contribution of hoverflies in predator diets. Short COI primers, previously used in diet analysis of insectivorous arthropods, will be validated in silico based on known prey taxa (hoverflies, wasps, bees, crop pests) and sequenced using in-house Illumina MiSeq and custom library preparation protocols.
In addition to diet analysis, the student will screen blood samples from wild birds for antibodies to the venom of stinging Hymenoptera using anti -IgY, IgA and IgM immunoassays. These assays will utilize both complete venom preparations and purified venom components. Birds which have been stung by wasps, honeybees or bumblebees develop antibodies that can be detected for many months. Evidence of antibodies will provide an indication of ecological interactions between birds and beneficial insects, and will also allow us to evaluate the hypothesis that birds avoid mimetic hoverflies because of costly interactions with hymenopteran "models". The student may choose to explore this hypothesis further with behavioural experiments testing the responses of birds with known antibody profiles to 3D models of mimetic and non-mimetic hoverflies.
Overall, we aim to provide insights into the importance of ecological and evolutionary links between hoverflies, other beneficial invertebrates, and avian predators. The results will help us understand the likely impact of biological control of pest insects, and the value of agri-environment schemes in boosting farm biodiversity.