Differential induction of plant chemical defenses by parasitized and unparasitized herbivores: consequences for reciprocal, multitrophic interactions

Insect parasitoids can play ecologically important roles in virtually all terrestrial plant–insect herbivore interactions, yet whether parasitoids alter the defensive traits that underlie interactions between plants and their herbivores remains a largely unexplored question. Here, we examined the reciprocal trophic interactions among populations of the wild cabbage Brassica oleracea that vary greatly in their production of defensive secondary compounds – glucosinolates (GSs), a generalist herbivore, Trichoplusia ni, and its polyembryonic parasitoid Copidosoma floridanum. In a greenhouse environment, plants were exposed to either healthy (unparasitized), parasitized, or no herbivores. Feeding damage by herbivores induced higher levels of the indole GSs, glucobrassicin and neoglucobrassicin, but not any of the other measured GSs. Herbivores parasitized by C. floridanum induced cabbage plants to produce 1.5 times more indole GSs than levels induced by healthy T. ni and five times more than...寄生性昆虫在几乎所有陆生植物-昆虫植食者互作中均发挥着关键的生态学功能，但寄生蜂是否会改变支撑植物与其植食者之间互作的防御性状，仍是一个尚未得到充分探索的科学问题。本研究针对防御性次生代谢产物——硫代葡萄糖苷（glucosinolates，GSs）合成差异显著的野生甘蓝（Brassica oleracea）种群、广食性植食者粉纹夜蛾（Trichoplusia ni）及其多胚生殖寄生蜂佛罗里达多胚跳小蜂（Copidosoma floridanum）之间的双向营养互作展开了探究。本实验在温室环境中开展，将植株分为三组：未受植食者取食组、健康（未被寄生）植食者取食组以及被寄生植食者取食组。植食者取食会诱导植株合成更高水平的吲哚类硫代葡萄糖苷：葡萄糖芸苔素（glucobrassicin）与新葡萄糖芸苔素（neoglucobrassicin），但对其余被测硫代葡萄糖苷无显著诱导效果。被佛罗里达多胚跳小蜂寄生的植食者，可诱导甘蓝合成的吲哚类硫代葡萄糖苷水平是健康粉纹夜蛾取食诱导水平的1.5倍，且较……