Mechanisms and consequences of change in aquatic protist communities

变化在自然界无处不在。然而，在过去几十年中，由于人为影响，环境变化的速度大大加快。我们对这种快速变化如何影响复杂的自然群落知之甚少，特别是群落级反应背后的实际机制是什么。例如，非生物变化是否对群落产生直接影响，或者是否通过某些物种或营养水平间接作用于多营养食物网？由此产生的群落结构差异可能影响生态动态和稳定性。即使在短时间内，社区也可能表现出对环境变化的进化反应。最终，这些变化可能对社区功能产生强烈影响。然而，我们对这些过程的有限理解妨碍了对自然生态系统变化后果的可靠预测。在此，我们建议以多营养原生生物群落为模型系统，研究环境变化对自然群落的影响。这些复杂的组合发生在热带山坡上沿强烈自然环境变化梯度的凤梨科植物的小型水生生境中。它们非常适合拟议的项目，因为它们可以在现场复制和操作，但也可以在受控条件下简化为实验室实验。在这个项目中，我们将首先在野外调查中确定驱动哥斯达黎加北部凤梨科原生生物群落结构沿海拔梯度变化的因素。随后，我们将使用专门设计的实地实验来测试和量化这些因素对自然群落及其功能的影响。在本实验中，我们将通过单独操纵和某些组合来检查直接非生物和间接生物（自上而下和自下而上）驱动因素。我们将直接将这些实地研究与实验室实验联系起来，使用我们在柏林自由生物研究所培养的凤梨原生物种。第一个实验室实验将明确考虑群落动态和稳定性，研究多种环境因素变化导致的生态变化机制。第二个实验室实验侧重于对环境变化作出反应的进化动力学。我们将测量某些原生生物系的可塑性和快速进化，并确定这些过程对共存、群落结构和生态系统功能的影响。在这个项目中，我们的目标是确定和测试影响自然群落的环境变化的关键方面，并揭示它们运作的机制。最终，这些知识将使我们能够预测生态系统及其功能变化的后果。

Change is ubiquitous in nature. However, rates of environmental change have accelerated strongly over the last few decades as a result of anthropogenic impacts. We know relatively little about how this rapid change affects complex natural communities, and in particular what the actual mechanisms behind community-level responses are. For example, does abiotic change have a direct community impact or do effects operate indirectly via certain species or trophic levels in multitrophic food webs? The resulting differences in community structure potentially affect ecological dynamics and stability. Communities might also show evolutionary responses to environmental change, even over short time frames. Ultimately, these changes could have strong impacts on community functions. However, our limited understanding of these processes precludes robust predictions of consequences of change for natural ecosystems.Here, we propose to use multitrophic protist communities as a model system to study the effects of environmental change on natural communities. These complex assemblages occur in small aquatic habitats in bromeliad plants along strong natural gradients of environmental change on tropical mountain slopes. They are ideally suited for the proposed project because they can be replicated and manipulated in the field but also simplified for lab experiments under controlled conditions.In this project, we will first identify those factors in a field survey that drive changes in bromeliad protist community structure along elevational gradients in Northern Costa Rica. We will subsequently use a field experiment specifically designed to test and quantify effects of those factors on natural communities and their functions. In this experiment, we will examine direct abiotic and indirect biotic (top-down and bottom-up) drivers by manipulating them both in isolation and in certain combinations.We will directly link these field studies with lab experiments using bromeliad protist species that we have in culture at the Institute of Biology, Freie Universität Berlin. The first lab experiment will address mechanisms of ecological change as a result of multiple changing environmental factors, explicitly considering community dynamics and stability. The second lab experiment focuses on evolutionary dynamics in response to environmental change. We will measure plasticity and rapid evolution in certain lines of protists, and determine effects of these processes on coexistence, community structure and ecosystem function.With this project, we aim to identify and test key aspects of environmental change affecting natural communities and reveal mechanisms by which they operate. Ultimately, this knowledge will put us in the position to predict consequences of change for ecosystems and their functions.