Hafer-Hahmann Nina, Vorburger Christoph
EAWAG, Swiss Federal Institute of Aquatic Science and Technology Dübendorf Switzerland.
Department of Biology University of Konstanz Konstanz Germany.
Ecol Evol. 2024 Mar 7;14(3):e11090. doi: 10.1002/ece3.11090. eCollection 2024 Mar.
How does diversity in nature come about? One factor contributing to this diversity are species interactions; diversity on one trophic level can shape diversity on lower or higher trophic levels. For example, parasite diversity enhances host immune diversity. Insect protective symbionts mediate host resistance and are, therefore, also engaged in reciprocal selection with their host's parasites. Here, we applied experimental evolution in a well-known symbiont-aphid-parasitoid system to study whether parasitoid diversity contributes to maintaining symbiont genetic diversity. We used caged populations of black bean aphids (), containing uninfected individuals and individuals infected with different strains of the bacterial endosymbiont , which protects aphids against parasitoids. Over multiple generations, these populations were exposed to three different species of parasitoid wasps (, or ), simultaneous or sequential mixtures of these species or no wasps. Surprisingly, we observed little selection for in most treatments, even when it clearly provided protection against a fatal parasitoid infection. This seemed to be caused by high induced costs of resistance: aphids surviving parasitoid attacks suffered an extreme reduction in fitness. In marked contrast to previous studies looking at the effect of different genotypes of a single parasitoid species, we found little evidence for a diversifying effect of multiple parasitoid species on symbiont diversity in hosts.
自然界中的多样性是如何产生的？物种间的相互作用是造成这种多样性的一个因素；一个营养级的多样性可以塑造较低或较高营养级的多样性。例如，寄生虫多样性会增强宿主的免疫多样性。昆虫保护性共生体介导宿主抗性，因此也与宿主的寄生虫进行相互选择。在这里，我们在一个著名的共生体-蚜虫-寄生蜂系统中应用实验进化，以研究寄生蜂多样性是否有助于维持共生体的遗传多样性。我们使用了黑豆蚜（）的笼养种群，其中包含未感染个体以及感染了不同菌株细菌内共生体的个体，该共生体可保护蚜虫免受寄生蜂侵害。在多代时间里，这些种群被暴露于三种不同的寄生蜂物种（、或）、这些物种的同时或相继混合组合，或者不接触任何寄生蜂。令人惊讶的是，我们在大多数处理中几乎没有观察到对的选择，即使它明显提供了针对致命寄生蜂感染的保护。这似乎是由高诱导抗性成本导致的：在寄生蜂攻击中存活下来的蚜虫适应性极度降低。与之前研究单一寄生蜂物种不同基因型影响的研究形成鲜明对比的是，我们几乎没有发现证据表明多种寄生蜂物种对宿主中共生体多样性有多样化影响。
