1. The direct and indirect impacts that invasive predators have on communities within their invaded range are poorly understood, particularly in the early stages of invasion. Through top‐down control of their prey, predators have the capacity to trigger cascading effects on lower trophic levels.
2. We found the recent arrival of the invasive paper wasp Polistes dominula Christ has been associated with substantial declines in local butterfly abundance in New Zealand. One of the butterfly species we observed to be affected is the monarch, Danaus plexippus Linnaeus with densities reduced by 66% at the study site. Field experiments were conducted to examine the strength of the predation pressure exerted by P. dominula on monarch caterpillars and the cascading effects on milkweed (Gomphocarpus physocarpus E. Mey.) fitness.
3. A survival study of monarch caterpillars was conducted across three habitat types (coastal, forest, and suburban). Caterpillar survival in suburban areas was lowest, with only 45% of caterpillars remaining after just 6 h of exposure to wasp foraging. Predation by P. dominula explained 85% of caterpillar deaths within the trial period.
4. The cascading effects of P. dominula presence were quantified through changes in the height, foliage, and reproductive output of milkweed plants. Monarch caterpillar predation by P. dominula was found to have a positive effect on milkweed fitness.
5. This study demonstrates a strong trophic cascade initiated by an invasive predator. These findings highlight the impacts an invasive species can have on local communities beyond their direct predatory effects.

中文翻译：

---

有入侵性的黄蜂对帝王蝶的寄主植物有很强的级联作用

1. 人们对入侵性掠食者对其入侵范围内的社区所产生的直接和间接影响知之甚少，尤其是在入侵的早期阶段。通过自上而下地控制猎物，捕食者有能力在较低营养级引发连锁反应。
2. 我们发现入侵性黄蜂的新近出现是Polistes dominula Christ与新西兰当地蝴蝶丰度的大幅下降有关。我们观察到受影响的蝴蝶物种之一是君主Danaus plexippus Linnaeus，其研究地点的密度降低了66％。进行了野外试验，以研究野豌豆对帝王毛虫施加的捕食压力的强度，以及对乳草（Gomphocarpus physocarpus E. Mey。）适应性的级联效应。
3. 对三种栖息地类型（沿海，森林和郊区）进行了帝王毛虫的生存研究。郊区的毛毛虫存活率最低，仅在暴露于黄蜂觅食6小时后才剩下45％的毛毛虫。P. dominula的捕食解释了试验期内85％的毛毛虫死亡。
4. 通过乳草植物的高度，枝叶和生殖产量的变化，可以定量确定斑节对虾存在的级联效应。P. dominula的帝王毛毛虫捕食对乳草的适应性具有积极作用。
5. 这项研究表明入侵性掠食者引发了强烈的营养级联反应。这些发现凸显了入侵物种可能对当地社区造成的影响，不仅仅是其直接的掠夺性影响。