Data from: The effect of trap colour and trap-flower distance on prey and pollinator capture in carnivorous Drosera species

1. The functional features of carnivorous plants’ traps have been mostly interpreted as adaptations to capture prey. Carnivorous plants that feed on insects, however, run the risk that increasing trapping effectiveness might in turn reduce reproductive success through capture of pollinators. Such a pollinator-prey conflict might play an important role in the evolution of trap features. In carnivorous plants with sticky leaves (e.g. Drosera, Pinguicula) both spatial distance between traps and flowers and their visual signals (e.g. colour, display size) likely play a role in attracting prey but it has also been suggested that they affect the risk of potential pollinators landing on a trap. It has been reported, for example, that red pigmentation in carnivorous plants may lure insect prey to traps. This idea remains controversial, however, because colour vision of most insects does not extend very far into the red part of the spectrum. 2. We tested an alternative hypothesis, namely that red pigmentation of the trapping leaves may reduce the risk of a pollinator-prey conflict. Experiments were conducted in a natural habitat of Drosera arcturi and D. spatulata in the Southern Alps of New Zealand. Using sticky model traps similar in shape to Drosera leaf traps and flowers, we investigated the effect of colour (green vs. red vs. white), and flower-trap distance (flower stalk length and leaf arrangement i.e. upright as in D. arcturi vs. flat ground rosette as in D. spatulata) on composition and abundance of insects landing and being trapped. 3. Flower-trap distance had no significant effect on the risk of pollinators being trapped but model flowers higher above the ground received more pollinator landings. Across all model traps the number of trapped potential pollinators was significantly lower in traps with red leaves compared to green ones. 4. The results suggest that the typical red pigmentation of the trapping leaves in Drosera may be a way to protect pollinators from being attracted and captured. However, our data also suggest that pollinator protection via red traps may come with a trade-off since total prey capture was also significantly reduced.

1. 食肉植物捕虫结构的功能特征，大多被解读为针对猎物捕获的适应性演化。不过，以昆虫为食的食肉植物面临潜在风险：捕虫结构的捕抓效能提升，可能会通过误捕传粉昆虫而降低繁殖成功率。这类传粉者-猎物冲突（pollinator-prey conflict），或许在捕虫结构的演化进程中发挥了关键作用。在具有粘性叶片的食肉植物（如茅膏菜属（Drosera）、捕虫堇属（Pinguicula））中，捕虫结构与花朵间的空间距离，以及二者的视觉信号（如色彩、展示尺寸），既可在吸引猎物过程中发挥功能，也有研究指出其会影响潜在传粉昆虫降落在捕虫结构上的风险。例如，已有研究报道食肉植物的红色色素沉着可将昆虫猎物引诱至捕虫结构，但该观点仍存在争议，原因在于多数昆虫的色觉光谱范围并未延伸至红光波段。2. 我们验证了一项替代性假说：捕虫叶片的红色色素沉着或可降低传粉者-猎物冲突的风险。实验在新西兰南阿尔卑斯山的自然栖息地中开展，实验对象为高山茅膏菜（Drosera arcturi）与匙叶茅膏菜（Drosera spatulata）。我们采用形态与茅膏菜叶片捕虫结构相似的粘性模型捕虫器，探究了色彩（绿色、红色及白色）以及花-捕虫结构距离（花茎长度与叶片排列方式，具体分为两类：一类如同高山茅膏菜的直立型，另一类如同匙叶茅膏菜的贴地莲座型）对降落在模型上并被捕获的昆虫的组成与丰度的影响。3. 花-捕虫结构距离对传粉昆虫被捕获的风险无显著影响，但离地更高的模型花朵能获得更多传粉昆虫降落。在所有模型捕虫器中，带有红色叶片的模型捕获的潜在传粉昆虫数量显著低于绿色叶片模型。4. 研究结果表明，茅膏菜属植物捕虫叶片典型的红色色素沉着，或为一种保护传粉昆虫免受吸引与捕获的策略。不过本研究数据同时显示，通过红色捕虫结构实现的传粉者保护可能存在权衡代价，因为总猎物捕获量也出现了显著下降。