Are aphid-resistant GM crops likely to be effective, and environmentally and evolutionarily sustainable?

Rationale
This exciting, multidisciplinary project will investigate the interplay among volatile-producing plants, crop pests and their natural enemies, and tests whether aphid-resistant GM crops are effective, and environmentally and evolutionarily sustainable. Sustainably increasing food production means intensifying the yield of production systems, while preserving in the long-term the environmental resources and ecosystem services they rely on. One way to improve crop production with a fixed amount of resources is to more effectively resist major yield-reducing crop pests such as aphids. Recent research has demonstrated the feasibility of genetically engineering important crop plants (wheat), to produce aphid alarm pheromones ((E)-ß-farnesene) naturally emitted by some plants as a defensive lure against aphids (Yu et al. 2012). The use of aphid-resistant genetically modified crops has potential benefits, but there are also concerns about the likely effectiveness of the proposed technique in the short- and long-term. For example, aphid alarm pheromone is used as a kairomone by aphid predators such as ladybirds to locate resource patches in the landscape (Francis et al. 2004). The indirect impacts of (E)-ß-farnesene-producing GM wheat on natural enemies of aphids such as ladybirds is currently unknown, but such indirect impacts may result in undesirable ecosystem consequences of GM wheat.
The project will therefore investigate relationships between pheromone-emitting GM wheat and ladybirds as an experimental system to identify risks of disrupting coevolved plant-pest-natural enemy systems. The student will test whether pests and their predators may evolve to ignore volatile cues in GM systems because the signals produced by these plans are ‘dishonest’. For example, an unintended effect of decoupling the cues normally used by predators to locate prey from actual prey availability may be that response to the kairomone becomes counter-selected in the ladybird predator, reducing the effectiveness of natural enemies in protecting both GM and non-GM crops against aphids. Furthermore, the student will evaluate whether widespread deployment of aphid-resistant crops – luring aphid predators to low-resource patches – could result in a decline of predator populations through a process known as “ecological trap” (Schlaepfer et al. 2002). In the longer term, evolutionary responses may be expected in the pest, as seen with resistance to pesticides – aphids are expected to stop responding to the alarm pheromone, reducing the effectiveness GM crops.
Workplan
The student will 1) Estimate evolutionary potential of laboratory-reared aphids’ and ladybirds’ behavioural response to pheromone, using an experimental evolution approach in controlled conditions; 2) Carry out behavioural experiments to characterise aphid and ladybird movements in response to different mixing proportions of pheromone-producing and non-producing plants; 3) Use individual-based modelling to integrate experimental data and simulate a plant-pest-natural enemy system, allowing the prediction of population and micro-evolutionary responses under different scenarios of GM crop deployment in the landscape.
Skills development
By pursuing these complementary approaches, the student will tackle key fundamental questions about the role of coevolution in trophic systems and critically evaluate an economically-important GM crop that is currently under active research and development. The student will be able to develop a broad range of skills by working with a team of researchers contributing cutting-edge expertise in data integration and individual based modelling of agricultural systems (Dr. Cornulier; Prof. Travis), plant communication (Prof. Johnson), animal behaviour (Dr Lucy Gilbert, JHI) and experimental evolution in crop pests (Dr. Lancaster). We will provide training in experimental design, basic and advanced data analysis and programming, plant and invertebrate ecology, chemical ecology, and mathematical modelling. The project will be based at the University of Aberdeen, where the student will benefit from local interaction with scientists at James Hutton Institute and Rowett Institute of Nutrition and Health, as well as a thriving U. of Aberdeen-based community of postgraduate students, postdocs, and faculty in ecology and plant and soil sciences.