Data from: Experimental evolution of parasitoid infectivity on symbiont-protected hosts leads to the emergence of genotype-specificity

Host-parasitoid interactions may lead to strong reciprocal selection for traits involved in host defense and parasitoid counter-defense. In aphids, individuals harboring the facultative bacterial endosymbiont Hamiltonella defensa exhibit enhanced resistance to parasitoid wasps. We used an experimental evolution approach to investigate the ability of the parasitoid wasp Lysiphlebus fabarum to adapt to the presence of H. defensa in its aphid host Aphis fabae. Sexual populations of the parasitoid were exposed for eleven generations to a single clone of A. fabae, either free of H. defensa or harboring artificial infections with three different isolates of H. defensa. Parasitoids adapted rapidly to the presence of H. defensa in their hosts, but this adaptation was in part specific to the symbiont isolate they were evolving against and did not result in an improved infectivity on all symbiont-protected hosts. Comparisons of life history traits among the evolved lines of parasitoids did not reveal any evidence for costs of adaptation to H. defensa in terms of correlated responses that could constrain such adaptation. These results show that parasitoids readily evolve counter-adaptations to heritable defensive symbionts of their hosts, but that different symbiont strains impose different evolutionary challenges. The symbionts thus mediate the host-parasite interaction by inducing line-by-line genetic specificity.

宿主与寄生蜂的相互作用，通常会对宿主防御及寄生蜂反防御相关性状产生强烈的往复选择压力。在蚜虫类群中，携带有兼性细菌内共生体汉密尔顿氏防御菌（Hamiltonella defensa）的个体，对寄生蜂的抗性显著增强。本研究采用实验进化（experimental evolution）方法，探究寄生蜂黑蚜茧蜂（Lysiphlebus fabarum）适应其宿主蚕豆蚜（Aphis fabae）体内H. defensa的能力。研究中将该寄生蜂的有性种群分别暴露于两种蚕豆蚜克隆系：一组不携带H. defensa，另一组则人工感染了3株不同的H. defensa分离株，持续暴露11个世代。结果显示，寄生蜂能够快速演化出适应宿主体内H. defensa的策略，但这种适应性在一定程度上与其所应对的共生体分离株特异性相关，并未使其对所有受共生体保护的宿主均提升侵染能力。对进化后的寄生蜂品系的生活史性状进行比较分析后发现，未发现任何证据表明，适应H. defensa的适应性存在相关响应代价，进而限制此类演化过程。本研究结果表明，寄生蜂可轻易演化出针对宿主可遗传防御共生体的反适应策略，但不同的共生菌株会带来不同的进化挑战。由此可见，共生菌通过诱导品系间的遗传特异性，介导了宿主与寄生物之间的相互作用。