Data from: Which traits do observers use to distinguish Batesian mimics from their models?

Batesian mimicry, in which a harmless mimic resembles a more aversive model, can encompass a wide range of morphological traits, but the resemblance is never perfect. Previous studies have used abstract “prey” designs to show that differences in certain traits may not be relevant to mimicry if they are not perceived or recognized by a predator. Here, we extend these results by examining how human “predators” respond to realistic variation in traits of aposematic wasps and their hoverfly mimics. We measured the ability of humans to discriminate between images of wasps and hoverflies in which only certain traits were visible, to determine the contributions of those traits to discrimination decisions. We found that shape is a particularly useful and easily learnt trait for separating the 2 taxa. Subjects did not successfully discriminate on the basis of abdominal patterns, despite those containing useful information. Color similarity between wasps and hoverflies is relatively high in comparison with other traits, suggesting that selection has acted more strongly on color. Our findings demonstrate the importance of consideration of natural variation in the traits of prey and their salience to predators for understanding the evolution of prey defenses.

贝氏拟态（Batesian mimicry）指无害的拟态者模仿具有更强厌恶性的模型物种，其拟态可涵盖多样的形态特征，但二者的相似性从未臻于完美。既往研究多采用抽象化的“猎物”模型开展实验，证实若某类特征无法被捕食者感知或识别，则其对拟态过程并无实质贡献。本研究通过探究人类“捕食者”对警戒态黄蜂（aposematic wasps）及其食蚜蝇拟态类群的特征自然变异的响应，拓展了前述研究结论。我们通过测量人类区分仅特定特征可见的黄蜂与食蚜蝇图像的能力，明确了各特征对分类判别决策的贡献程度。研究发现，形态轮廓是区分两类群尤为实用且易于习得的判别特征。尽管腹部斑纹包含有效判别信息，但受试者无法仅凭该特征完成二者的区分。相较于其他特征，黄蜂与食蚜蝇的颜色相似度相对更高，这表明自然选择对体色的选择压力更强。本研究结果表明，若要阐明猎物防御机制的演化历程，需充分考量猎物特征的自然变异及其对捕食者的感知显著性。