The role of predator-prey naïveté for the invasion success of lady beetles - A comparison of species interactions across two continents

入侵物种对全球生物多样性构成重大威胁。尽管关于入侵物种有害影响的科学文献越来越多，但我们往往缺乏对为什么一些物种变得具有侵略性而另一些物种保持良性的机制理解。特别是昆虫捕食者，是非本地动物群的重要组成部分。可能的是，入侵的捕食者可能不会被本地的顶级捕食者发现，因此受到较少的野生动物内部干扰（naïve捕食者假说）。此外，入侵掠食者可能受益于本土猎物缺乏对掠食者的躲避（naïve猎物假说）。识别非本地捕食者的能力，以及因此产生的内部干扰和捕食者回避的强度，预计取决于与本地捕食者的线索相似性。拥有一组独特线索的非本地捕食者可能具有naïve猎物和naïve捕食者的双重优势，从而胜过本地捕食者。瓢虫作为防治蚜虫的生物制剂被有意地重新分布在各大洲，有一种瓢虫在两个大陆入侵。一些蚜虫物种受到蚂蚁的保护，而另一些蚜虫则进化出了一种针对瓢虫的典型反捕食行为（例如从植物上掉下来）。由于强大的营养相互依赖关系以及类似（入侵范围内的同类物种）和新的（入侵范围内没有同类物种）非本地瓢虫物种的可用性，蚁-瓢虫-蚜虫系统特别适合于测试捕食者-猎物naïveté。在这里，我们将比较蚂蚁对瓢虫的攻击，蚜虫的回避行为，以及目前在欧洲和北美发生的瓢虫对蚜虫的消耗。比较与欧洲瓢虫在其本土和入侵范围内的相互作用，将揭示这些相互作用的差异是否有助于入侵的成功。此外，我们将分析瓢虫线索，量化本地和非本地物种之间的线索相似性。行为实验与化学分析的结合使我们能够验证捕食者-猎物naïveté假说。洲际方法对于评估捕食者-被捕食者对非本地物种入侵成功的重要性至关重要。该项目将通过将物种相互作用与本地和非本地物种之间的线索相似性联系起来，进一步有助于对生物入侵的一般机制理解。这种联合方法不仅将阐明介导这些相互作用的化学物质，而且还将提高我们解释和预测昆虫捕食者高影响入侵的能力。

Invasive species pose a major threat to global biodiversity. Despite the growing scientific literature on detrimental effects of invasive species, we often lack a mechanistic understanding why some species become invasive while others remain benign. Insect predators, in particular, represent a significant portion of the non-native fauna. Possibly, invasive predators might remain undetected by native top-predators and thus suffer less intraguild interference (naïve predator hypothesis). In addition, invasive predators might benefit from the lack of predator avoidance by native prey (naïve prey hypothesis). The ability to recognize non-native predators and consequently the strength of intraguild interference and predator avoidance is expected to depend on cue similarity with native predators. Non-native predators bearing a unique set of cues might have the double advantage of naïve prey and naïve predators and thus outcompete native predators.Lady beetles have been intentionally redistributed across continents as biocontrol agents against aphids, with one species being invasive in two continents. Some aphid species are protected by ants, while others have evolved a characteristic antipredator behavior against lady beetles (e.g. dropping from plants). Due to the strong trophic interdependence and the availability of similar (congeneric species in the invaded range) and novel (no congeneric species in the invaded range) non-native lady beetle species, the ant-lady beetle-aphid system is particularly well suited to test for predator-prey naïveté. Here, we will compare the aggression of ants towards lady beetles, the avoidance behavior of aphids, and the consumption of aphids by lady beetles currently occurring in Europe and in North America. The comparison of interactions with European lady beetles in their native and in the invaded range will reveal whether differences in these interactions contribute to the invasion success. In addition, we will analyze lady beetle cues to quantify cue similarity between native and non-native species. The combination of behavioral experiments with chemical analyses enables us to test the predator-prey naïveté hypothesis.The intercontinental approach is crucial to evaluate the importance of predator-prey naiveté for the invasion success of a non-native species. The proposed project will further contribute to a general mechanistic understanding of biological invasions by relating species interactions to the cue similarity between native and non-native species. This joint approach will not only shed light on the semiochemicals that mediate these interactions but also improve our ability to explain and predict high-impact invasions of insect predators.