Henry Youn, Dahirel Maxime, Wallisch Jesper, Ginesi Sandro, Vorburger Christoph
Eawag - Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
University of Lausanne, Department of Ecology and Evolution, Lausanne, Switzerland.
J Evol Biol. 2025 Jun 26. doi: 10.1093/jeb/voaf083.
Parasitoids are important natural enemies of insects, imposing strong selection for the evolution of resistance. In aphids, the heritable defensive endosymbiont Hamiltonella defensa is a key determinant of resistance, making symbiont-conferred defense a potential target for specific adaptation by parasitoids. We tested this hypothesis in the aphid parasitoid Lysiphlebus fabarum and four of its host species, Aphis fabae fabae, A. hederae, A. urticata, and A. ruborum. The parasitoids show host-associated genetic differentiation indicative of host specialization, and each of these aphid species harbors 1-3 distinct strains of H. defensa, with no shared strains. We introduced eight H. defensa strains from all four aphid species into a common host background (a laboratory strain of symbiont-free A. f. fabae) and then tested the ability of 35 field-collected L. fabarum lines from the same four hosts to parasitize the H. defensa-carrying aphids. The natural origin of symbionts was a key determinant of parasitism success, with strains from A. f. fabae and A. hederae conferring strong protection, and strains from A. urticata and A. ruborum providing virtually no protection. For one strain each from A. f. fabae and A. hederae, we found a signature of specific adaptation by parasitoids, as parasitoids able to overcome their protection mostly came from the same hosts as the symbiont strains. Two other strains were so strongly protective that they permitted very little parasitism independent of where parasitoids came from. While not fully conclusive, these results are consistent with specialized parasitoids adapting to certain defensive symbionts of their host species, supporting the notion of symbiont-mediated coevolution.
寄生蜂是昆虫的重要天敌，对昆虫抗性的进化施加了强大的选择压力。在蚜虫中，可遗传的防御性内共生菌汉密尔顿ella defensa是抗性的关键决定因素，使得共生菌介导的防御成为寄生蜂特异性适应的潜在目标。我们在蚜虫寄生蜂豌豆蚜茧蜂及其四个寄主物种，即豆蚜、常春藤蚜、荨麻蚜和悬钩子蚜中检验了这一假设。这些寄生蜂表现出与寄主相关的遗传分化，表明其寄主专一化，并且这些蚜虫物种中的每一个都携带1至3种不同的H. defensa菌株，没有共享菌株。我们将来自所有四个蚜虫物种的八种H. defensa菌株引入一个共同的寄主背景（一种无共生菌的豆蚜实验室菌株），然后测试了来自相同四个寄主的35个田间采集的豌豆蚜茧蜂品系寄生携带H. defensa的蚜虫的能力。共生菌的自然来源是寄生成功的关键决定因素，来自豆蚜和常春藤蚜的菌株提供了强大的保护，而来自荨麻蚜和悬钩子蚜的菌株几乎没有提供保护。对于来自豆蚜和常春藤蚜的各一个菌株，我们发现了寄生蜂特异性适应的迹象，因为能够克服其保护作用的寄生蜂大多来自与共生菌菌株相同的寄主。另外两个菌株的保护作用非常强，以至于无论寄生蜂来自何处，它们都很少被寄生。虽然这些结果并不完全具有决定性，但与专门的寄生蜂适应其寄主物种的某些防御性共生菌一致，支持了共生菌介导的共同进化的观点。
