Data from: Evolutionary contribution to coexistence of competitors in microbial food webs

The theory of species coexistence is a key concept in ecology that has received much attention. The role of rapid evolution for determining species coexistence is still poorly understood although evolutionary change on ecological time-scales has the potential to change almost any ecological process. The influence of evolution on coexistence can be especially pronounced in microbial communities where organisms often have large population sizes and short generation times. Previous work on coexistence has assumed that traits involved in resource use and species interactions are constant or change very slowly in terms of ecological time-scales. However, recent work suggests that these traits can evolve rapidly. Nevertheless, the importance of rapid evolution to coexistence has not been tested experimentally. Here, we show how rapid evolution alters the frequency of two bacterial competitors over time when grown together with specialist consumers (bacteriophages), a generalist consumer (protozoan) and all in combination. We find that consumers facilitate coexistence in a manner consistent with classic ecological theory. However, through disentangling the relative contributions of ecology (changes in consumer abundance) and evolution (changes in traits mediating species interactions) on the frequency of the two competitors over time, we find differences between the consumer types and combinations. Overall, our results indicate that the influence of evolution on species coexistence strongly depends on the traits and species interactions considered.物种共存理论是生态学中广受关注的核心概念。尽管生态时间尺度上的演化变化几乎能够改变所有生态过程，但快速演化在决定物种共存中的作用仍未得到充分阐明。演化对物种共存的影响在微生物群落中尤为显著，因为这类群落中的生物往往种群规模庞大且世代时长较短。以往关于物种共存的研究均假定，参与资源利用与物种互作的性状在生态时间尺度上保持恒定或变化极缓。然而近期研究表明，这些性状可发生快速演化。尽管如此，快速演化对物种共存的重要性尚未通过实验得到验证。本研究探讨了当两种细菌竞争者分别与专性捕食者（specialist consumer，即噬菌体bacteriophages）、广食性捕食者（generalist consumer，即原生动物protozoan）单独共培养，或同时与两类捕食者共同培养时，快速演化如何随时间推移改变二者的相对频率。我们发现，捕食者促进物种共存的模式符合经典生态学理论。不过，通过拆解分析生态过程（捕食者丰度变化）与演化过程（介导物种互作的性状改变）对两种竞争者随时间变化的相对贡献，我们发现不同捕食者类型及其组合间存在显著差异。总体而言，本研究结果表明，演化对物种共存的影响在很大程度上取决于所考量的性状与物种互作类型。