Data from: Biased generalization of salient traits drives the evolution of warning signals

The importance of receiver biases in shaping the evolution of many signalling systems is widely acknowledged. Here we show that receiver bias can explain which traits evolve to become warning signals. For warning colouration, a generalization bias for a signalling trait can result from predators learning to discriminate unprofitable from profitable prey. However, since the colour patterns of prey are complex traits with multiple components, it is crucial to understand which of the many aspects of prey appearance evolve into signals. We provide experimental evidence that the more salient differences in prey traits give rise to greater generalization bias, corresponding to stronger selection towards trait exaggeration. Our results are based on experiments with domestic chickens as predators in a Skinner-box-like setting, and imply that the difference in appearance between profitable and unprofitable prey that is most rapidly learnt produces the greatest generalization bias. As a consequence, certain salient traits of unprofitable prey are selected towards exaggeration to even higher salience, driving the evolution of warning colouration. This general idea may also help to explain the evolution of many other striking signalling traits found in nature.

接收者偏倚（receiver biases）在塑造众多信号系统演化进程中的重要性已获广泛认可。本研究证实，接收者偏倚可解释哪些性状会演化成为警戒信号。针对警戒色（warning colouration）而言，捕食者学习区分可盈利猎物与不可盈利猎物的过程，可能催生针对信号性状的泛化偏倚（generalization bias）。但由于猎物色斑属于兼具多重组成部分的复杂性状，明确猎物外观的诸多维度中，究竟哪些会演化成为信号，是至关重要的课题。我们通过实验证明，猎物性状间的显著性差异会引发更强的泛化偏倚，对应着针对性状夸张化的更强选择压力。本研究结果基于以家鸡作为捕食者、在类斯金纳箱（Skinner box）环境中开展的实验，研究表明：可盈利猎物与不可盈利猎物间的外观差异，其习得速度越快，引发的泛化偏倚越强。据此，不可盈利猎物的某些显著性性状会被选择向更高显著性的夸张方向演化，进而推动警戒色的演化。这一通用理论或可用于解释自然界中诸多其他引人注目的信号性状的演化历程。