Data from: The role of predators in maintaining the geographic organization of aposematic signals

Selective predation of aposematic signals is expected to promote phenotypic uniformity. But while uniform within a population, numerous species display impressive variations in warning signals among adjacent populations. Predators from different localities learning to avoid distinct signals while performing intense selection on others are thus expected to maintain such a geographic organization. We tested this assumption by placing clay frog models, representing distinct color morphs of the Peruvian poison-dart frog Ranitomeya imitator and a non conspicuous frog, reciprocally between adjacent localities. In each locality, avian predators were able to discriminate between warning signals; the adjacent exotic morph suffered up to four times more attacks than the local one and two times more than the non conspicuous phenotype. Moreover, predation attempts on the exotic morph quickly decreased to almost nil, suggesting rapid learning. This experiment offers direct evidence for the existence of different predator communities performing localized homogenizing selection on distinct aposematic signals.

对警戒色信号（aposematic signals）的选择性捕食，理论上应推动表型均一性（phenotypic uniformity）的形成。但即便同一种群内部的警戒色信号保持均一，众多物种在相邻种群间却展现出显著的警告信号变异。据此推测，来自不同地域的捕食者在学会规避特定信号的同时，对其他信号施加强烈选择压力，有望维持这种地理分布格局。我们通过在相邻地域间交叉放置黏土蛙模型（clay frog models）对该假设进行验证：这些模型分别代表秘鲁模仿箭毒蛙（Ranitomeya imitator）的不同体色变型（color morphs），以及一种隐蔽色蛙类。在每个试验地域，鸟类捕食者均可区分不同的警告信号；相邻区域的外来色型所受攻击次数最多可达本地色型的4倍，为隐蔽色表型（non conspicuous phenotype）的2倍。此外，针对外来色型的捕食尝试迅速降至近乎为零，这表明捕食者能够快速完成学习过程。本实验为不同捕食者群落对不同警戒色信号实施局域化均质选择的现象，提供了直接证据。