An experimental evolution test of signalling theory

The natural world is filled with examples of signalling or communication between individuals. Males attract females with showy ornaments or repel rivals with loud roars, offspring beg from their parents, ants release chemicals to coordinate foraging behaviours and poisonous caterpillars warn their predators away with bright colours.

Although the advantages of signalling may seem obvious, it actually poses a problem for evolutionary theory. The problem is why don't individuals lie or exaggerate, to their own benefit. For example, why don't all male peacocks signal that they are the best quality mate, or why don't all chicks signal that they are the hungriest? Put simply, what keeps signals honest? If signals were dishonest, then the best strategy would be to ignore them, and so the signalling system would be lost.

Evolutionary theory has proposed a number of ways in which signals could be kept honest, and there is an excellent empirical literature on this, examining traits that range from birds tails, to facial markings in wasps, to the roars of deer, to eyespan of flies, to begging in chicks. However, the nature of working on signalling in animals limits what kinds of experiments are possible.

Here we will take advantage of the fact that bacteria signal to each other, to coordinate cooperative behaviours, in order to test very general theory about how signalling will evolve. We will manipulate factors such as the extent to which honesty is favoured, block signalling, enhance signalling and then follow the evolutionary consequences. Furthermore, because we are working on bacteria, we can follow the consequences at all levels from the behaviour to the gene.

Overall, our aim is to examine how the social and ecological environment influences the evolution of communication. This work is not an alternative to working on animals, but rather a complementary way to get at different aspects of the same questions.

Furthermore, our work has potential medical consequences, because bacterial signalling controls the behaviours that determine how well pathogenic bacteria grow, how virulent they are in their hosts, and how well they resist antibiotics. Consequently, by examining the consequences for these pathogenic behaviours, we will also collect data that is a necessary first step in determining whether signalling can be exploited as a medical intervention strategy.

This is a multidisciplinary project empirically testing fundamental principles of signalling theory. The project combines molecular expertise with evolutionary theory and this enables us, for the first time, to experimentally test how signalling systems evolve over a number of generations. The use of bacteria as a model system allows us to manipulate signalling in a way that is not possible with more traditional study organisms (e.g. birds and mammals).

The major impact of the work will be the research output, and the work will be of interest to the fields of microbiology, animal behaviour and evolutionary biology. The work will provide new insights into signalling systems and the mechanisms behind them, and will complement and enhance the body of work already performed in the animal field.

Quorum sensing regulates virulence in our organism Pseudomonas aeruginosa, and so our work will also have applied consequences and be of interest to applied microbiologists and clinicians. Demonstrating how signalling systems evolve will provide unique insights into infection, and how virulence and antibiotic resistance can develop.

The project will provide excellent training for a post-doctoral researcher who will benefit greatly from multidisciplinary collaborative research and who will receive training in paper writing, a wide variety of methodologies and experimental design and analysis. They will also be encouraged to apply for an independent fellowship at the end of the project.

We will aim to publicise our findings in a timely manner in high quality international ranked journals to maximize the impact of the research as well as presenting the work at major international conferences.

We will also disseminate the research on our personal and university websites. Where possible we will engage in public communication such as television and radio programmes and popular science magazines.

The sequence and transcriptomic data generated will be deposited with EMBL/Genbank and also be used to update genome annotations in public databases such as National Centre for Biotechnology Information (NCBI) and The Pseudomonas Genome Project. This will provide invaluable information for scientists working on all aspects of Pseudomonas biology.