Assessing how air pollution interrupts insect sex pheromone signaling

Common air pollutants such as ozone (O3) and nitrogen oxides (NOx) can indirectly impair the fitness of plants and insects by chemically altering the odour compounds that they use for communication. In our latest NERC-funded research, we designed a novel prototype field facility, to investigate the impact of air pollutants upon important ecological processes, particularly pollination. Our preliminary results identified a 90% reduction in flower visitation by pollinators under moderate increases in O3 and NOx, indicating an unexpectedly severe (relative to those predicted by laboratory studies and simulation models) negative impact upon insect-provided pollination.

Recent funding from the NERC Capital call is enabling us to iterate upon this prototype to create a permanent Free-Air Diesel and Ozone Enrichment (FADOE) research platform at the University of Reading's Sonning Farm, with the primary goal of investigating empirically how air pollution interferes with chemical communication. This globally unique platform will provide the student with an unprecedented opportunity for novel research.

Insects use chemical communication for a broader range of interactions than simply locating floral resources, for example, mate location using sex pheromones. Our previous laboratory research has demonstrated that sex pheromones are also vulnerable to chemical degradation by air pollutants. However, the mechanisms by which sex pheromones and floral attractants operate and convey information differ significantly. Floral signals commonly consist of a mixture of tens of compounds (many of which are ubiquitous between species) in relatively large volume over a long duration. In contrast, sex pheromones are commonly comprised of few (usually 1-3) temporally-limited compounds (emissions cease once a mate is found), whose ratio are critical for signal recognition. Thus, degradation of pheromones by air pollution is likely to result in potentially more dramatic effects upon insect behavioural ecology.

This PhD project, providing the first mechanistic field-scale investigation into the effects of common air pollutants on insect pheromone communication, will consist of three distinct but interrelated work packages:

WP1. Field-scale impacts of diesel exhaust and ozone on the ability of insects to detect and orient towards pheromones (FIELD ECOLOGY)
Our NERC-funded FADOE platform will be used to quantify the impact of air pollution on mate-finding ecology of a broad range of insect species, with differing life history strategies and pheromone chemistry. This will be achieved using both commercially available pheromone lures and traps baited with live insects.

WP2. Laboratory-based mechanistic insect behavioural studies (BEHAVIOURAL ECOLOGY)
Those insects most disrupted by pollution in WP1 will be investigated in laboratory assays to dissect the mechanisms by which disruption occurs. Using our new custom-built wind-tunnel, in-flight behaviour will be studied under different-pollution scenarios.

WP3. Chemical analysis of changes to pheromones in field and laboratory (PHEROMONE CHEMISTRY)
Linking WP1 and 2, we will chemically quantify the extent of odour degradation. A Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-TOFMS) will be used to analyse, for the first time in any study, the degradation of signalling molecules in real-time under field conditions. Quantification of pheromone degradation in WP2 will be conducted using gas chromatography-mass spectrometry.