Collaborative Research: The role of branching complexity in driving food chain length in rivers

几十年来，生态学家一直对食物链长度变化的起源感兴趣。食物链长度是指食物网中从生产者到最高消费者的食物链数量。了解食物链长度的控制是很重要的，因为它会影响通过生态系统的能量流动和人类经常消费的顶级捕食者中的污染物浓度。普遍的观点认为，食物链的长度是由生态系统的大小决定的。大型生态系统可以提供更多的基础资源，支持更大规模的组成物种，和/或减轻环境变化的影响。然而，虽然在空间简单的系统（例如，海洋岛屿和湖泊），但在空间上较为复杂的系统中，如分支河流网络中，没有明确的支持。在空间复杂的系统中，生态系统大小假说的混合结果意味着存在被忽视的因素，控制食物链的长度。该项目将探讨生态系统复杂性作为生态系统动态中一个关键因素的作用。具体来说，研究人员将专注于河流网络的分支复杂性，并研究其在推动食物链长度方面的重要性。该项目的广泛影响包括以下内容。首先，研究人员将通过与K-12学校的正式合作伙伴关系参与外展活动。第二，该项目将为代表性不足的少数群体和一名博士后科学家提供研究培训机会。最后，研究人员将通过在线知识库分发开源软件，以促进研究产品的应用。该项目将联合收割机结合理论和实证方法来验证以下假设：（1）复杂的河流网络，具有更高的分支水平，支持长的食物链，因为有更多的分支（即，（2）河流（流域）生态系统的规模对食物链长度的影响很小，因为环境异质性与生态系统规模之间的关联取决于具体情况。研究人员将开发一系列数学模型，以预测食物链长度与分支复杂性/生态系统大小之间的关联。理论预测将通过对地球仪现有的食物链长度和环境协变量数据集进行荟萃分析来验证。总的来说，该项目将提供重要的见解如何生态群落结构在空间复杂的systems.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

The origin of variation in food chain length - the number of feeding links from producers to apex consumers in a food web - has intrigued ecologists for decades. Understanding controls of food chain length is important because it influences energy flow through ecosystems and contaminant concentrations in top predators that humans often consume. The prevailing thought has held that food chain length is determined by the size of an ecosystem. Large ecosystems can provide greater amounts of basal resources, support larger population sizes of constituent species, and/or mitigate the impact of environmental changes. However, while ample empirical evidence for the ecosystem size hypothesis exists in spatially simple systems (e.g., oceanic islands and lakes), there is less clear support in more spatially complex systems, such as branching river networks. The mixed results for the ecosystem size hypothesis in spatially complex systems imply the existence of overlooked factors that control food chain length. The project will explore the role of ecosystem complexity that is emerging as a key factor in ecosystem dynamics. Specifically, researchers will focus on the branching complexity of river networks and investigate its importance in driving food chain length. The broader impacts of this project include the following components. First, researchers will participate in outreach events through formal partnerships with K-12 schools. Second, the project will provide research training opportunities for underrepresented minorities and a postdoctoral scientist. Lastly, researchers will distribute open-source software through online repositories to facilitate the application of research products.The project will combine theoretical and empirical approaches to test the following hypotheses: (1) complex river networks, with greater levels of branching, support long food chains because having more branches (i.e., tributary systems) with distinct geological and/or climatic backgrounds may provide diverse habitats that buffer the impact of environmental fluctuations; (2) ecosystem size in rivers (watershed area) has weak effects on food chain length due to the context-dependent association between environmental heterogeneity and ecosystem size. Researchers will develop a series of mathematical models to generate predictions for the association between food chain length and branching complexity/ecosystem size. Theoretical predictions will be validated by meta-analyses of existing datasets of food chain length and environmental covariates across the globe. Overall, the project will provide important insights into how ecological communities are structured in spatially complex systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.