Steven Saw, Uefune Masayoshi, Ozawa Rika, Takabayashi Junji, Kainoh Yooichi
Master's Program in Education, University of Tsukuba, Tsukuba, Ibaraki, 305-8572, Japan.
Department Agrobiological Resources, Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan.
J Chem Ecol. 2019 Apr;45(4):402-409. doi: 10.1007/s10886-019-01064-6. Epub 2019 Mar 11.
In nature, parasitoid wasps encounter and sometimes show oviposition behavior to nonhost species. However, little is known about the effect of such negative incidences on their subsequent host-searching behavior. We tested this effect in a tritrophic system of maize plants (Zea mays), common armyworms (hosts), tobacco cutworms (nonhosts), and parasitoid wasps, Cotesia kariyai. We used oviposition inexperienced C. kariyai and negative-experienced individuals that had expressed oviposition behavior toward nonhosts on nonhost-infested maize leaves. We first observed the olfactory behavior of C. kariyai to volatiles from host-infested plants or nonhost-infested plants in a wind tunnel. Negative-experienced wasps showed significantly lower rates of taking-off behavior (Step-1), significantly longer duration until landing (Step-2), and lower rates of landing behavior (Step-3) toward nonhost-infested plants than inexperienced wasps. However, the negative-experience did not affect these three steps toward host-infested plants. A negative experience appears to have negatively affected the olfactory responses to nonhost-infested plants. The chemical analyses suggested that the wasps associated (Z)-3-hexenyl acetate, a compound that was emitted more in nonhost-infested plants, with the negative experience, and reduced their response to nonhost-infested plants. Furthermore, we observed that the searching duration of wasps on either nonhost- or host-infested plants (Step-4) was reduced on both plant types after the negative experiences. Therefore, the negative experience in Step-4 would be nonadaptive for wasps on host-infested plants. Our study indicated that the density (i.e., possible encounters) of nonhost species as well as that of host species in the field should be considered when assessing the host-searching behavior of parasitoid wasps.
在自然界中，寄生蜂会遇到非寄主物种，有时还会对其表现出产卵行为。然而，对于这种负面事件对其后续寄主搜索行为的影响，我们知之甚少。我们在一个包括玉米植株（玉米）、粘虫（寄主）、烟草夜蛾（非寄主）和寄生蜂卡里亚茧蜂的三营养系统中测试了这种影响。我们使用了没有产卵经验的卡里亚茧蜂以及在非寄主侵染的玉米叶片上对非寄主表现出产卵行为的有负面经验的个体。我们首先在风洞中观察了卡里亚茧蜂对寄主侵染植物或非寄主侵染植物挥发物的嗅觉行为。有负面经验的黄蜂对非寄主侵染植物表现出明显更低的起飞行为率（步骤1）、显著更长的着陆前持续时间（步骤2）以及更低的着陆行为率（步骤3）。然而，负面经验并未影响对寄主侵染植物的这三个步骤。负面经验似乎对非寄主侵染植物的嗅觉反应产生了负面影响。化学分析表明，黄蜂将在非寄主侵染植物中释放量更多的一种化合物——醋酸（Z）-3-己烯酯与负面经验联系起来，并降低了对非寄主侵染植物的反应。此外，我们观察到，在经历负面经验后，黄蜂在非寄主或寄主侵染植物上的搜索持续时间（步骤4）在两种植物类型上都减少了。因此，步骤4中的负面经验对寄主侵染植物上的黄蜂来说是不适应的。我们的研究表明，在评估寄生蜂的寄主搜索行为时，应考虑田间非寄主物种以及寄主物种的密度（即可能的相遇情况）。
