Spillover of bacteria from agriculture into the surrounding soilscape

人类现在耕种着地球上近40%的无冰土地。在如此短的时间内，土地覆盖的这种极端变化在地球历史上是史无前例的，而且众所周知，它会导致物种灭绝，改变物种的进化轨迹。然而，我们几乎所有关于这些环境影响的知识都来自于对地面上的植物或动物的研究。相比之下，人们对土壤微生物的影响知之甚少，尽管这些物种在分解、养分循环、碳固存和维持农业所依赖的土壤肥力方面发挥了关键作用。事实上，虽然我们知道微生物有可能在很长的距离内扩散，但我们甚至缺乏对微生物扩散的一般了解，或者现代景观中自然和农业系统的安排如何影响土壤生物多样性。景观结构对植物、脊椎动物和无脊椎动物的影响已经研究了几十年，但直到最近几年，研究土壤微生物的技术才足够充分和负担得起，可以在下面进行类似的研究。除了导致物种灭绝和改变它们之间的相互作用外，农业就像一个环境过滤器，只允许某些物种存活。此外，在已经肥沃的土壤上添加肥料时，养分的高度可获得性为那些能够迅速吸收养分并耐受恶劣农业条件和杀虫剂等化学品的物种提供了宝贵的回报。这种受到严重限制的生态系统具有潜在的高回报，是自然选择的肥沃土壤。因此，我们已经看到了农业杂草和害虫对杀虫剂耐药性的进化，以及微生物对抗生素耐药性的进化。这样的例子可能只是冰山一角，然而微生物在农业中进化的程度，以及这如何影响土壤生态系统的功能，在很大程度上仍然是未知的。更重要的是，就像杂草可以蔓延到农作物，抗生素耐药性传播到人类疾病一样，在农业中进化的生物有可能在整个景观中传播，包括进入自然区域。我们最近已经证明，高产的农业栖息地会产生大量的昆虫，然后这些昆虫会“溢出”到附近的自然栖息地，并改变生态系统的功能。该项目将测试类似的过程是否发生在土壤微生物中，更重要的是，农业集约化是否推动土壤微生物的进化和农业选择的基因在整个景观中的传播。然后，我们将测试这种溢出的后果，并传播生态系统运行的方式。

Humans now farm almost 40 percent of the Earth's ice-free land. This extreme change in land cover over such a short time is unprecedented in the planet's history, and it is well known to drive extinctions and alter the evolutionary trajectories of species. Yet nearly all of our knowledge of these environmental effects comes from research on plants or animals above ground. In contrast, the effects on soil micro-organisms are poorly understood, despite the key role of these species in decomposition, nutrient cycling, carbon sequestration, and the maintenance of soil fertility on which agriculture depends. In fact, while we know that microbes have the potential to disperse over long distances, we lack even a general understanding of microbial dispersal, or how the arrangement of natural and agricultural systems in modern landscapes affects soil biodiversity. The influence of landscape structure on plants, vertebrates and invertebrates has been studied for decades, but only in recent years has the technology for studying soil microbes been adequate and affordable enough to conduct comparable research belowground.In addition to driving extinctions of species and altering their interactions, agriculture acts like an environmental filter, only allowing certain species to survive. Furthermore, the high availability of nutrients when fertilizer is added to already fertile soils provides a valuable reward to those species that can rapidly take them up and tolerate the harsh agricultural conditions and chemicals such as pesticides. Such heavily constrained ecosystems, with potential high rewards, are fertile ground for natural selection. Therefore, we have seen the evolution of pesticide resistance in weeds and insect pests of agriculture, and the evolution of antibiotic resistance in microbes. Such examples are likely to be the tip of the iceberg, yet the extent to which microbes evolve in agriculture, and how this affects the functioning of soil ecosystems, remain largely unknown. More importantly, just as weeds can spread out of crops and antibiotic resistance has spread to human diseases, organisms that evolve in agriculture have the potential to spread across the landscape including into natural areas. We have recently demonstrated that highly-productive agricultural habitats generate an abundance of insects, which then 'spill over' into nearby natural habitats and alter the functioning of ecosystems. This project will test whether similar processes occur in soil microbes and, more importantly, whether the intensification of agriculture drives the evolution of soil microbes and the spread of agriculturally-selected genes across the landscape. We will then test the consequences of this spillover and spread for the ways in which ecosystems function.