Vengeful Vines: Cell Death and Neoplasm Formation in Aristolochia (Aristolochiaceae, Piperales) in Response to Oviposition of Troidini (Papilionidae, Lepidoptera) Butterflies

ABSTRACT The ecological interactions of the iconic Troidini swallowtail butterflies and their host plants remain largely unknown, despite the popularity of these butterflies in collections and their significance as conservation flagships. We sought to elucidate the ecological interactions of perhaps the least known life‐stage of the butterflies: that of the egg with its host plant. We recorded oviposition location and egg survival rates for Troides helena, Troides amphrysus and Pachliopta antiphus on their host plants Aristolochia acuminata and Aristolochia cf. foveolata through systematic monitoring of the Poring Butterfly Garden (Sabah, Malaysia). Here, we make the first observation of hypersensitive response (HR)‐like cell death and neoplasm formation in response to butterfly eggs deposited on Aristolochia leaves. This represents the first documented case of such egg‐killing traits in the highly diverse Magnoliids (> 10,000 spp.). HR‐like cell death under eggs showed a statistically significant negative effect on butterfly egg survival. Additionally, we provide a quantitative overview of the oviposition sites selected by Troidini, establishing that up to 37.6% of eggs are not oviposited on the host plant. Together, this suggests a fitness cost to butterflies and a possible behavioral avoidance mechanism. These findings on egg‐killing and oviposition behavior provide a significant contribution to the study of coevolutionary interactions between Troidini and Aristolochia . Furthermore, these observations provide valuable information for butterfly gardens and conservation projects, where egg‐killing by host plants may significantly impact butterfly survival. Overall, this research provides a unique egg‐based perspective on the ecological interactions between Troidini and their host plants.