Evolution of bacterial life history traits is sensitive to community structure

Very few studies have experimentally assessed the evolutionary effects of species interactions within the same trophic level. Here we show that when Serratia marcescens evolve in multispecies communities, their growth rate exceeds the growth rate of the bacteria that evolved alone, whereas the biomass yield gets lower. In addition to the community effects per se, we found that few species in the communities caused strong effects on S. marcescens evolution. The results indicate that evolutionary responses (of a focal species) are different in communities, compared to species evolving alone. Moreover, selection can lead to very different outcomes depending on the community structure. Such context dependencies cast doubt on our ability to predict the course of evolution in the wild, where species often inhabit very different kinds of communities.

鲜有研究通过实验评估同一营养级 (trophic level) 内物种互作对演化过程的影响。本研究发现，当粘质沙雷氏菌（Serratia marcescens）在多物种群落中发生演化时，其生长速率高于单独演化的该菌株，但其生物量产出则有所降低。除群落本身的效应外，我们还发现群落中仅有少数物种会对粘质沙雷氏菌的演化产生显著影响。研究结果表明，相较于单独演化的物种，群落环境中靶标物种的演化响应存在显著差异。此外，选择压力会因群落结构的不同而产生截然不同的演化结果。这类情境依赖性使得我们对预测野生环境中演化进程的能力产生了质疑——在野生环境中，物种往往栖息于多种多样的群落之中。