Conspicuous colours in animals are usually explained by mate attraction, predator avoidance and prey attraction. Predators may lure prey by mimicking food or other resources. Alternatively, some animals avoid predation by visually signalling unpalatability to predators. The evolution of a signal is affected by receiver processing mechanisms. Therefore, variation in sensory systems may explain the evolution of colour polymorphism of conspicuous species. We aimed to investigate the role of receivers in the evolution and maintenance of colour conspicuousness and polymorphism in Gasteracantha cancriformis (Araneidae). We tested two hypotheses: (1) conspicuous coloration is a prey lure strategy; (2) conspicuous coloration is a warning signal to predators. Furthermore, we identified the taxonomic order of prey captured and the type of predator (avian versus arthropod). To assess the role of prey, we conducted a field experiment in which webs were assigned to one of four treatments: yellow, red or black spider models, or no model. For each treatment, we counted the number of prey trapped on the webs and calculated the damaged area of the webs. To assess the role of predators, we conducted a second field experiment in which we attached yellow, red and black models to trees using nylon thread and observed the number of attack markings on each model. Our results did not corroborate the prey attraction hypothesis. In the predation experiment, black models had more attack markings, indicating that yellow and red models were less preferred. This suggests that spider coloration may play a role in predator avoidance. Colour polymorphism in this species is possibly a multifunctional attribute, where some morphs benefit from aposematism, whereas others may have alternative fitness advantages. Nonadaptive explanations should also be considered in future experiments of the evolution and maintenance of colour polymorphisms.

中文翻译：

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多态性天体网蜘蛛的显眼颜色：避免捕食者但不吸引猎物的证据

动物显眼的颜色通常可以用配偶吸引、捕食者回避和猎物吸引来解释。捕食者可能会通过模仿食物或其他资源来引诱猎物。或者，一些动物通过视觉上向捕食者发出不好吃的信号来避免捕食。信号的演变受接收机处理机制的影响。因此，感官系统的变化可以解释显眼物种颜色多态性的演变。我们旨在研究接收器在 Gasteracantha cancriformis (Araneidae) 中颜色显着性和多态性的进化和维持中的作用。我们测试了两个假设：（1）显眼的颜色是一种诱饵策略；(2)显眼的颜色是对捕食者的警告信号。此外，我们确定了捕获的猎物的分类顺序和捕食者的类型（鸟类与节肢动物）。为了评估猎物的作用，我们进行了一项现场实验，其中将网分配到四种处理中的一种：黄色、红色或黑色蜘蛛模型，或无模型。对于每次处理，我们计算了被困在网上的猎物数量，并计算了网的损坏面积。为了评估捕食者的作用，我们进行了第二次现场实验，其中我们使用尼龙线将黄色、红色和黑色模型连接到树上，并观察每个模型上攻击标记的数量。我们的结果没有证实猎物吸引力假设。在捕食实验中，黑色模型有更多的攻击标记，表明黄色和红色模型不太受欢迎。这表明蜘蛛的颜色可能在避免捕食者中发挥作用。该物种的颜色多态性可能是一种多功能属性，其中一些变体受益于禁行，而其他变体可能具有替代的适应性优势。在未来的颜色多态性演化和维持实验中，也应考虑非适应性解释。