The role of sex, climate change, and land use on the spread of aphid pesticide-resistance in the UK: a PhD project using transcriptomic and GIS-based

This project combines cutting-edge environmental modelling techniques with physiological and genomic analyses to understand the recent spread of insecticide-resistant grain aphids towards cooler climates in the UK. The student's work will inform environmental management options for controlling the spread of resistant clones, based on rigorous understanding of environmental drivers and physiological mechanisms. The work will also provide fundamental insight into the evolutionary process.

The evolution and spread of insecticide resistance in crop pest insects is both a major challenge for food security, and a major opportunity to understand the evolutionary process under conditions of environmental change. Aphids provide an ideal study system in this regard, because they exhibit rapid adaptation to both climate and pesticides, driven by their complex life cycles with both sexual and asexual phases (Fenton et al. 2010). Until recently, insecticide-resistant clonal lines of the grain aphid (Sitobion avenae) were restricted to the southern parts of the UK. In the last few years, however, warmer winters in the north of the UK have allowed clonal aphid lines to persist year around, and it is suspected that less severe winters combined with changing insecticide use patterns may facilitate overwintering of insecticide resistant clones in Scotland.

In this project we will address the following questions:

1) Why is insecticide-resistance limited to asexual clones of S. avenae?
2) Is there a physiological trade-off between insecticide resistance and cold-hardiness?
3) What are the environmental factors favouring the increase in successful, insecticide-resistant clones in Scotland, and how can we use this information to limit their spread?

To address these questions, the student will undertake:

1) Physiological and transcriptomic basis of resistance mechanisms and trade-offs. The student will expose field-collected resistant and susceptible clonal lines, as well as susceptible sexual lineages, to different combinations of insecticide exposure and temperature, to determine physiological consequences. Transcriptomic analysis of individuals from these treatment categories can reveal genetic basis for observed physiological trade-offs between cold resistance and insecticide resistance.

2) GIS and spatial modelling to understand the environmental drivers of clonal frequencies. For this, the student will rely on SASA's (the CASE partner) access to a large dataset on the frequency of resistant aphids in Scotland over the past several years. Data have been gathered by genotyping aphids captured in four suction traps located at various locations across the UK (http://www.rothamsted.ac.uk/insect-survey/about). Using microsatellite DNA, sampled aphids can be attributed to previously described resistant and susceptible strains (Foster et al. 2015).

Using the novel GIS-based approach of joint species distribution modelling (JDSM), the student will correlate aphid resistance with climate and weather patterns, land use, insecticide use, and the total abundances of S. avenae and other aphid species in the collections.

The student will be based at the University of Aberdeen, in the dynamic Institute of Biological & Environmental Sciences, a world-leading institute for environmental and agricultural science. There the student will join the research group of Dr Lesley Lancaster (www.lancasterlab.weebly.com). Ongoing projects in the group involve genomic techniques, joint species distribution modelling, and experimental evolution to understand community interactions, pest dynamics, and niche evolution under climate change. The co-supervisor on the project is Dr Gaynor Malloch of the James Hutton Institute (JHI) in Dundee. Dr Malloch an expert in aphid biology, and JHI is a world-leading research institute for food security. The student will also liaise regularly with the Entomology team at SASA in Edinburgh to gather data.