Are aphid parasitoids locally adapted to the prevalence of defensive symbionts in their hosts?

Background: Insect parasitoids are under strong selection to overcome their hosts’ defences. In aphids, resistance to parasitoids is largely determined by the presence or absence of protective endosymbionts such as Hamiltonella defensa. Hence, parasitoids may become locally adapted to the prevalence of this endosymbiont in their host populations. To address this, we collected isofemale lines of the aphid parasitoid Lysiphlebus fabarum from 17 sites in Switzerland and France, at which we also estimated the frequency of infection with H. defensa as well as other bacterial endosymbionts in five important aphid host species. The parasitoids’ ability to overcome H. defensa-mediated resistance was then quantified by estimating their parasitism success on a single aphid clone (Aphis fabae fabae) that was either uninfected or experimentally infected with one of three different isolates of H. defensa. Results: The five aphid species (Aphis fabae fabae, A. f. cirsiiacanthoides, A. hederae, A. ru...研究背景：昆虫寄生蜂面临强烈的选择压力以克服宿主的防御机制。在蚜虫类群中，对寄生蜂的抗性主要由汉密尔顿氏菌（Hamiltonella defensa）这类保护性内共生菌的有无决定。因此，寄生蜂可能会对宿主种群中该内共生菌的流行率产生局部适应性。为探究这一问题，我们从瑞士与法国的17个采样点收集了蚜茧蜂（Lysiphlebus fabarum）的单雌系，并同步估算了5种重要蚜虫宿主中感染汉密尔顿氏菌及其他细菌内共生菌的频率。随后，我们以单个豆蚜指名亚种（Aphis fabae fabae）克隆系为测试宿主，分别设置未感染组与实验感染了3种不同汉密尔顿氏菌分离株的感染组，通过量化寄生成功率来测定寄生蜂克服汉密尔顿氏菌介导抗性的能力。研究结果：5种蚜虫（Aphis fabae fabae、A. f. cirsiiacanthoides、A. hederae、A. ru...