Department of Ecology & Evolution, University of Chicago, Chicago, Illinois, USA
Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA.
mBio. 2019 Sep 3;10(5):e01703-19. doi: 10.1128/mBio.01703-19.
Intraspecific variation in plant nutrient and defensive traits can regulate ecosystem-level processes, such as decomposition and transformation of plant carbon and nutrients. Understanding the regulatory mechanisms of ecosystem functions at local scales may facilitate predictions of the resistance and resilience of these functions to change. We evaluated how riverine bacterial community assembly and predicted gene content corresponded to decomposition rates of green leaf inputs from red alder trees into rivers of Washington State, USA. Previously, we documented accelerated decomposition rates for leaves originating from trees growing adjacent to the site of decomposition versus more distant locales, suggesting that microbes have a "home-field advantage" in decomposing local leaves. Here, we identified repeatable stages of bacterial succession, each defined by dominant taxa with predicted gene content associated with metabolic pathways relevant to the leaf characteristics and course of decomposition. "Home" leaves contained bacterial communities with distinct functional capacities to degrade aromatic compounds. Given known spatial variation of alder aromatics, this finding helps explain locally accelerated decomposition. Bacterial decomposer communities adjust to intraspecific variation in leaves at spatial scales of less than a kilometer, providing a mechanism for rapid response to changes in resources such as range shifts among plant genotypes. Such rapid responses among bacterial communities in turn may maintain high rates of carbon and nutrient cycling through aquatic ecosystems. Community ecologists have traditionally treated individuals within a species as uniform, with individual-level biodiversity rarely considered as a regulator of community and ecosystem function. In our study system, we have documented clear evidence of within-species variation causing local ecosystem adaptation to fluxes across ecosystem boundaries. In this striking pattern of a "home-field advantage," leaves from individual trees tend to decompose most rapidly when immediately adjacent to their parent tree. Here, we merge community ecology experiments with microbiome approaches to describe how bacterial communities adjust to within-species variation in leaves over spatial scales of less than a kilometer. The results show that bacterial community compositional changes facilitate rapid ecosystem responses to environmental change, effectively maintaining high rates of carbon and nutrient cycling through ecosystems.
植物营养和防御特性的种内变异可以调节生态系统水平的过程，如植物碳和养分的分解和转化。了解局部尺度上生态系统功能的调节机制，可以促进对这些功能对变化的抵抗力和恢复力的预测。我们评估了河流细菌群落组成和预测基因含量与美国华盛顿州河流中来自红桤木树叶输入的分解速率之间的对应关系。此前，我们记录到来自靠近分解地点的树木的树叶的分解速度比来自更远地方的树木的树叶更快，这表明微生物在分解当地树叶方面具有“主场优势”。在这里，我们确定了细菌演替的可重复阶段，每个阶段都由与与叶片特征和分解过程相关的代谢途径相关的预测基因含量有关的优势分类群定义。“本地”叶片中含有具有独特功能能力的细菌群落，可以降解芳香族化合物。鉴于已知的桤木芳香族化合物的空间变异，这一发现有助于解释局部加速分解的原因。细菌分解者群落可以根据不到一公里的空间尺度调整叶片的种内变异，为快速响应资源变化（例如植物基因型之间的范围转移）提供了一种机制。细菌群落之间的这种快速响应反过来又可以通过水生生态系统维持高碳和养分循环速率。群落生态学家传统上将一个物种内的个体视为均匀的，很少考虑个体水平的生物多样性作为群落和生态系统功能的调节者。在我们的研究系统中，我们已经记录了明显的证据，证明种内变异导致了当地生态系统适应生态系统边界的通量。在这种明显的“主场优势”模式中，当个体树叶与其亲树相邻时，最容易迅速分解。在这里，我们将群落生态学实验与微生物组方法相结合，描述了细菌群落如何在不到一公里的空间尺度上适应叶片的种内变异。结果表明，细菌群落组成变化促进了生态系统对环境变化的快速响应，有效地维持了通过生态系统的高碳和养分循环速率。
