Host–parasite interactions often fuel coevolutionary change. However, parasitism is one of a myriad of possible ecological interactions in nature. Biotic (for example, predation) and abiotic (for example, temperature) variation can amplify or dilute parasitism as a selective force on hosts and parasites, driving population variation in (co)evolutionary trajectories. We dissected the relationships between wider ecology and coevolutionary trajectory using 16 ecologically complex Daphnia magna–Pasteuria ramosa ponds seeded with an identical starting host (Daphnia) and parasite (Pasteuria) population. We show, using a time-shift experiment and outdoor population data, how multivariate biotic and abiotic ecological differences between ponds caused coevolutionary divergence. Wider ecology drove variation in host evolution of resistance, but not parasite infectivity; parasites subsequently coevolved in response to the changing complement of host genotypes, such that parasites adapted to historically resistant host genotypes. Parasitism was a stronger interaction for the parasite than for its host, probably because the host is the principal environment and selective force, whereas for hosts, parasite-mediated selection is one of many sources of selection. Our findings reveal the mechanisms through which wider ecology creates coevolutionary hotspots and coldspots in biologically realistic arenas of host–parasite interaction, and sheds light on how the ecological theatre can affect the (co)evolutionary play.

宿主与寄生虫的相互作用通常会促进共同进化的变化。然而，寄生是自然界中无数可能的生态相互作用之一。生物（例如，捕食）和非生物（例如，温度）变化可以放大或稀释寄生作为对宿主和寄生虫的选择力，推动（共同）进化轨迹中的种群变化。我们使用 16 个生态复杂的Daphnia magna – Pasteuria ramosa池塘剖析了更广泛的生态学和共同进化轨迹之间的关系，这些池塘接种了相同的起始宿主（水蚤）和寄生虫（Pasteuria ）） 人口。我们使用时移实验和室外种群数据展示了池塘之间的多变量生物和非生物生态差异如何导致共同进化分歧。更广泛的生态学推动了宿主抗性进化的变化，但不是寄生虫传染性；寄生虫随后共同进化以响应不断变化的宿主基因型，使得寄生虫适应历史上具有抗性的宿主基因型。寄生虫对寄生虫的相互作用比对宿主的相互作用更强，这可能是因为宿主是主要的环境和选择力，而对于宿主来说，寄生虫介导的选择是众多选择来源之一。我们的研究结果揭示了更广泛的生态学在宿主-寄生虫相互作用的生物学现实领域中创造共同进化热点和冷点的机制，