An experimental evolution test of signalling theory

自然界充满了个体之间的信号或通信的例子。雄性用华丽的装饰吸引雌性，或者用响亮的吼声击退对手，后代向父母乞讨，蚂蚁释放化学物质来协调觅食行为，有毒的毛虫用鲜艳的颜色警告捕食者。尽管信号的优势似乎显而易见，但它实际上给进化理论带来了一个问题。问题是，为什么人们不为了自己的利益而撒谎或夸大。例如，为什么不是所有的雄孔雀都发出它们是最佳伴侣的信号，或者为什么不是所有的小孔雀都发出它们是最饥饿的信号？简而言之，是什么让信号保持诚实？如果信号是不诚实的，那么最好的策略就是忽略它们，这样信号系统就会丢失，进化理论提出了许多保持信号诚实的方法，并且有一个很好的经验文献，研究了从鸟类尾巴到黄蜂面部标记，到鹿的咆哮，到苍蝇的眼睛，到小鸡的乞讨。然而，在动物中研究信号的性质限制了可能的实验类型。在这里，我们将利用细菌相互发送信号的事实来协调合作行为，以测试关于信号如何进化的非常普遍的理论。我们将操纵一些因素，比如诚实受到青睐的程度，阻止信号传递，增强信号传递，然后遵循进化的结果。此外，由于我们正在研究细菌，我们可以从行为到基因的各个层面上跟踪结果。总的来说，我们的目标是研究社会和生态环境如何影响通信的演变。这项工作并不是对动物研究的替代，而是对同一问题的不同方面的补充。此外，我们的工作具有潜在的医学后果，因为细菌信号控制着决定致病细菌生长状况的行为，它们在宿主中的毒性如何，以及它们对抗生素的抵抗力如何。因此，通过检查这些致病行为的后果，我们还将收集数据，这是确定信号是否可以作为医疗干预策略的必要的第一步。

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.