An experimental evolution test of signalling theory

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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.