Data from: Coarse dark patterning functionally constrains adaptive shifts from aposematism to crypsis in strawberry poison frogs

Ecological specialization often requires tight co-evolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the com-bined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations. We combined data from 17 natural populations of Straw-berry poison frogs, Oophaga pumilio with an experimental approach using digitalized images of frogs and chickens as predators. We show that bright coloration often co-occurs with coarse pat-terning among the natural populations. Dull green frogs with coarse patterning are rare in nature but in the experiment they were as easily detected as bright red frogs suggesting that this trait combination represent a transient evolutionary state towards aposematism. Hence, a gain of ei-ther bright color or coarse patterning leads to conspicuousness but a transition back to crypsis would be functionally constrained in populations with both bright color and coarse patterning by requiring simultaneous changes in two traits. Thus, populations (or species) signaling apose-matism by conspicuous color should be less likely to face an evolutionary dead-end and more likely to radiate than populations with both conspicuous color and coarse patterning.生态特化往往需要多个性状间的紧密协同进化，这可能会限制后续的演化路径，并使物种更易走向灭绝。警戒色（aposematism）与隐蔽（crypsis）是两类用于躲避捕食的特化适应策略。本研究旨在探究体色与斑纹对猎物显眼度的联合效应，是否会在功能上制约或促进这两类适应策略之间的演化转变。我们整合了17个草莓箭毒蛙（Oophaga pumilio）自然种群的数据，并采用以家鸡为捕食者、蛙类数字化图像为实验材料的实验方法。研究发现，在自然种群中，明亮体色往往与粗犷斑纹相伴出现。自然界中带有粗犷斑纹的暗绿色蛙类十分稀少，但在实验中它们的被捕食检出率与亮红色蛙类并无显著差异，这表明该性状组合代表了一种向警戒色演化的过渡性状态。因此，仅获得明亮体色或粗犷斑纹其一即可提升显眼度，但对于同时具备明亮体色与粗犷斑纹的种群而言，逆转为隐蔽策略的演化过程会受到功能上的制约——这需要同时改变两个性状。综上，与同时具备显眼体色与粗犷斑纹的种群相比，仅通过显眼体色传递警戒色信号的种群（或物种）更不易陷入演化死胡同，且更有可能发生辐射演化。