Data from: Batesian mimics influence the evolution of conspicuousness in an aposematic salamander

Conspicuousness, or having high contrast relative to the surrounding background, is a common feature of unpalatable species. Several hypotheses have been proposed to explain the occurrence of conspicuousness, and while most involve the role of conspicuousness as a direct signal of unpalatability to potential predators, one hypothesis suggests that exaggerated conspicuousness may evolve in unpalatable species to reduce predator confusion with palatable species (potential Batesian mimics). This hypothesis of antagonistic coevolution between palatable and unpalatable species hinges on the ‘cost of conspicuousness,’ in which conspicuousness increases the likelihood of predation more in palatable species than in unpalatable species. Under this mimicry scenario four patterns are expected: 1) mimics will more closely resemble local models than models from other localities, 2) there will be a positive relationship between mimic and model conspicuousness, 3) models will be more conspicuous in the presence of mimics, and 4) when models and mimics differ in conspicuousness, mimics will be less conspicuous than models. We tested these predictions in the salamander mimicry system involving Notophthalmus viridescens (model) and one color morph of Plethodon cinereus (mimic). All predictions were supported, indicating that selection for Batesian mimicry not only influences the evolution of mimics, but also the evolution of the models they resemble. These findings indicate that mimicry plays a large role in the evolution of model warning signals, particularly influencing the evolution of conspicuousness.

醒目性（Conspicuousness），即与周围背景形成高对比度的特性，是不可口物种的典型特征。学界已提出多种假说以解释醒目性的演化：多数假说认为醒目性可作为直接信号，向潜在捕食者传递物种不可口的信息；但其中一种假说提出，不可口物种可能演化出过度醒目性，以此降低捕食者将其与可口物种（即潜在贝茨拟态者（Batesian mimics））混淆的概率。
该针对可口与不可口物种间拮抗协同进化（antagonistic coevolution）的假说，其核心立足于“醒目性成本”（cost of conspicuousness）：即醒目性对可口物种的捕食风险提升幅度，显著高于不可口物种。在该拟态场景下，可预期出现四种模式：
1. 拟态者与本地模型物种的相似度，将高于其与其他地域模型物种的相似度；
2. 拟态者与模型的醒目性呈正相关关系；
3. 在拟态者存在的场景中，模型物种的醒目性会更高；
4. 当模型与拟态者的醒目性存在差异时，拟态者的醒目性将低于模型物种。
我们在以Notophthalmus viridescens（作为模型物种）与Plethodon cinereus的一种色型（作为拟态者）构成的蝾螈拟态系统中，对上述预测进行了检验。所有预测均得到了实证支持，这表明贝茨拟态（Batesian mimicry）的选择压力不仅影响拟态者的演化，同时也作用于其拟态的模型物种。本研究结果显示，拟态在模型物种的警戒信号演化中扮演了关键角色，尤其对醒目性的演化具有显著调控作用。