Wissenschaftskolleg zu Berlin, Wallotstraße 19, Berlin, Germany.
Evolutionary Biology, Universität Bielefeld, Konsequez 45, Bielefeld, 33615, Germany.
Biol Rev Camb Philos Soc. 2021 Dec;96(6):2446-2460. doi: 10.1111/brv.12760. Epub 2021 Jun 15.
Warning signals are a striking example of natural selection present in almost every ecological community - from Nordic meadows to tropical rainforests, defended prey species and their mimics ward off potential predators before they attack. Yet despite the wide distribution of warning signals, they are relatively scarce as a proportion of the total prey available, and more so in some biomes than others. Classically, warning signals are thought to be governed by positive density-dependent selection, i.e. they succeed better when they are more common. Therefore, after surmounting this initial barrier to their evolution, it is puzzling that they remain uncommon on the scale of the community. Here, we explore factors likely to determine the prevalence of warning signals in prey assemblages. These factors include the nature of prey defences and any constraints upon them, the behavioural interactions of predators with different prey defences, the numerical responses of predators governed by movement and reproduction, the diversity and abundance of undefended alternative prey and Batesian mimics in the community, and variability in other ecological circumstances. We also discuss the macroevolution of warning signals. Our review finds that we have a basic understanding of how many species in some taxonomic groups have warning signals, but very little information on the interrelationships among population abundances across prey communities, the diversity of signal phenotypes, and prey defences. We also have detailed knowledge of how a few generalist predator species forage in artificial laboratory environments, but we know much less about how predators forage in complex natural communities with variable prey defences. We describe how empirical work to address each of these knowledge gaps can test specific hypotheses for why warning signals exhibit their particular patterns of distribution. This will help us to understand how behavioural interactions shape ecological communities.
警告信号是自然选择在几乎每一个生态群落中存在的一个显著例子——从北欧草地到热带雨林，防御性猎物及其拟态物种在潜在捕食者发动攻击之前就会对其进行防御。然而，尽管警告信号分布广泛，但相对于可用猎物总数来说，它们的比例相对较少，在某些生物群系中比其他生物群系更为稀少。传统上，警告信号被认为受到正密度依赖选择的支配，也就是说，当它们更为普遍时，它们的生存成功率更高。因此，在克服了它们进化的最初障碍之后，令人困惑的是，它们在群落尺度上仍然很少见。在这里，我们探讨了可能决定猎物组合中警告信号流行程度的因素。这些因素包括猎物防御的性质及其任何限制、不同猎物防御的捕食者之间的行为相互作用、受运动和繁殖控制的捕食者的数量反应、群落中未防御的替代猎物和贝氏拟态的多样性和丰度，以及其他生态环境的可变性。我们还讨论了警告信号的宏观进化。我们的综述发现，我们对一些分类群中有多少物种具有警告信号有了基本的了解，但对猎物群落中种群丰度的相互关系、信号表型的多样性和猎物防御知之甚少。我们还详细了解了少数几种肉食性掠食者在人工实验室环境中觅食的方式，但我们对掠食者在具有可变猎物防御的复杂自然群落中如何觅食知之甚少。我们描述了如何开展实证工作来解决这些知识空白中的每一个，以检验为什么警告信号表现出特定分布模式的具体假设。这将有助于我们了解行为相互作用如何塑造生态群落。
