Raw data for: Captivating color: evidence for optimal stimulus design in a polymorphic prey lure

Many species – humans included – employ color as an instrument of deception. One intriguing example of this resides in the conspicuous abstract color patterns displayed on the bodies of female orb weaving spiders. These displays increase prey interception rates and thereby function at least as visual lures. Their chromatic properties however vary extensively, both across and within species, with discrete forms often co-existing in the manner of a stable polymorphism. Variation is principally expressed in terms of signal hue (color per se), but it is unclear how attractiveness scales with this property and if extant morphs are maximally attractive relative to a graded range of potential alternatives. We examined these questions by assessing catch rates among color-manipulated females of the dimorphic jeweled spider Gasteracantha fornicata in their natural webs. The manipulation altered dorsal appearance in a manner akin to adding six new variants of their existing white/yellow phenotypes. This magnified the natural variation in stimulus hue independently of chroma (saturation) across a range spanning most of the color spectrum. Catch rate varied across treatments in simple accordance with how greatly stimulus hue deviated from either of the two extant spider phenotypes. Predictions based upon fly-perceived chromatic and achromatic background contrast were clearly unsupported despite dipterans constituting ~60 % of identifiable prey. This study supports the importance of signal coloration per se in G. fornicata and suggests that extant lure phenotypes reside in a broadly optimal spectral range for stimulating their aggregate prey community.

众多物种——包括人类在内——均将色彩作为欺诈的工具。这一现象的有趣例证之一体现在雌性圆网蛛体表所展现的醒目抽象色彩图案。这些图案能够提高捕食效率，因而至少在视觉上起到诱饵的作用。然而，其色彩属性在物种之间以及物种内部均存在广泛的差异，不同形态常常以稳定的多态性共存。这种变化主要表现在信号色调（即色彩本身）上，但色彩吸引力与这一属性的比例尚不明确，以及现有的形态是否相对于潜在的广泛替代选择范围达到最大吸引力。我们通过评估在自然网中色彩操纵的雌性二态宝石蛛 Gasteracantha fornicata 的捕获率来探讨这些问题。这种操纵方式类似于为它们现有的白/黄表型添加了六种新的变体。这放大了刺激色调的自然变异，这种变异独立于色度（饱和度），覆盖了大部分光谱范围。捕获率在不同处理方法中简单按照刺激色调与两种现有蜘蛛形态之一的偏差程度而变化。基于苍蝇感知的色彩和无色彩背景对比的预测显然缺乏依据，尽管双翅目昆虫构成了可识别猎物的大约 60%。这项研究支持了信号色彩本身在 G. fornicata 中的重要性，并表明现有的诱饵形态位于一个广泛最优的光谱范围内，以刺激其聚集的捕食物种群。