Data from: Selection by parasitoid females among closely related hosts based on volatiles: Identifying relevant chemical cues

Parasitoid fitness is influenced by the ability to overcome host defense strategies and by the ability of parasitoid females to select high-quality host individuals. When females are unable to differentiate among hosts, their fitness will decrease with an increasing abundance of resistant hosts. To understand the effect of mixed host populations on female fitness, it is therefore necessary to investigate the ability of female parasitoids to select among hosts. Here, we used behavioral assays, headspace volatile collection, and electrophysiology to study the ability of Asecodes parviclava to use olfactory cues to select between a susceptible host (Galerucella calmariensis) and a resistant host (Galerucella pusilla) from a distance. Our studies show that parasitoid females have the capacity to distinguish the two hosts and that the selection behavior is acquired through experiences during earlier life stages. Further, we identified two volatiles (α-terpinolene and [E]-β-ocimene) which amounts differ between the two plant–herbivore systems and that caused behavioral and electrophysiological responses. The consequence of this selection behavior is that females have the capacity to avoid laying eggs in G. pusilla, where the egg mortality is higher due to much stronger immune responses toward A. parviclava than in larvae of G. calmariensis.

寄生蜂适合度（Parasitoid fitness）受其克服宿主防御策略的能力，以及雌性寄生蜂选择高质量宿主个体的能力共同影响。当雌性寄生蜂无法区分各类宿主时，随着抗性宿主种群丰度升高，其适合度将随之下降。为探明混合宿主种群对雌性寄生蜂适合度的影响，亟需探究雌性寄生蜂的宿主选择能力。

本研究采用行为实验法、顶空挥发性物质收集法与电生理检测技术，探究刻腹小蜂（Asecodes parviclava）能否通过嗅觉线索在远距离范围内区分易感宿主（欧洲荨麻叶甲 Galerucella calmariensis）与抗性宿主（北美车前叶甲 Galerucella pusilla）。研究结果表明，雌性寄生蜂具备区分这两类宿主的能力，且此类宿主选择行为源自其早期生活史阶段的经验习得。

此外，本研究鉴定出两种挥发性有机物：α-萜品油烯（α-terpinolene）与反式-β-罗勒烯（[E]-β-ocimene），二者在两种植物-植食性昆虫系统中的相对含量存在差异，并可引发寄生蜂的行为响应与电生理反应。此类宿主选择行为使得雌性寄生蜂能够避免在北美车前叶甲体内产卵：相较于欧洲荨麻叶甲幼虫，北美车前叶甲幼虫对刻腹小蜂（Asecodes parviclava）的免疫应答更强，因此寄生卵在其体内的死亡率显著更高。