Collaborative Research & RUI: Spatial Patch Structure: Can Ephemeral and Heterogeneous Resource Patches Influence Biotic Assemblages in Streams

在许多生态系统中，优势生境斑块的总体质量或资源水平经常发生变化。周期性地，栖息地斑块可能会受到物理上的破坏或破坏。在这种高度动态的系统中，人们通常认为移动动物对生境斑块的排列或其他景观属性没有反应。基本的逻辑是，动物群对景观属性的反应将被这种系统的空间和时间变异性所掩盖。在这项建议中，我们认为，高度动态系统中的移动动物实际上对景观属性--特别是斑块排列--做出了反应。斑块的质量和排列对斑块破坏或资源变化后的种群持久性和物种间的相互作用有很大影响。在之前的NSF资助的研究中，我们在实验室和野外实验中发现，溪流栖息的摇蚊和桡足类对栖息地(叶)斑块的质量和分布做出反应，但我们没有考虑斑块稳定性、斑块资源(叶物种)组成或捕食者-猎物相互作用对群落动态的影响。在这里，我们假设河床中的无脊椎动物丰度在多个斑块(景观)的尺度上比在单个斑块的尺度上得到更好的解释；与斑块排列、斑块稳定性和斑块质量的交互作用直接相关；无脊椎动物对这三个因素的响应被鱼类捕食者的存在所改变。我们提出了三个现场实验来检验以下具体假设：(1)在稳定的景观(没有斑块运动)中，溪流无脊椎动物的丰富度取决于斑块排列和斑块质量(树叶种类组成)；(2)当斑块不稳定时，无脊椎动物的丰度取决于斑块排列的交互作用和斑块的稳定性水平；(3)河流无脊椎动物对斑块排列、质量和稳定性的反应受捕食性鱼类的存在的影响。为了验证前两个假设，我们将使用重复测量析因设计来操纵斑块排列和斑块稳定性或叶片质量。对于第三个假设，我们将一次控制捕食者的丰度和一个景观属性(斑块排列、斑块稳定性或树叶质量)。我们将跟踪景观层面上无脊椎动物丰富度随时间的变化，尽管我们也将能够评估构成每个景观的各个斑块内部和之间的变异性。这项工作具有重要的意义，因为我们正在研究景观的变化--就斑块类型及其排列和资源水平而言--是否以及如何影响生物组合。目前对生物对空间景观特征响应的理解主要是基于景观特征相对稳定的系统的理论和实证工作。由于许多系统是高度动态的--补丁移动，补丁质量随时间变化--这里提出的研究类型是非常必要的。与我们之前的拨款一样，这项研究将由宾夕法尼亚州立大学伊利分校的P.Silver和大型研究机构马里兰大学帕克分校的M.A.Palmer共同努力进行。PI、本科生、研究生和博士后助理将在工作的所有阶段进行合作，从而为学生提供最大限度地参与高质量研究的机会，在一个大型研究校园和一个以教学为主的小型校园中，学生们在紧张的团队合作和合作的氛围中参与高质量的研究。

In many ecosystems, the dominant habitat patches frequently change in terms of their overall quality or their resource levels. Periodically, habitat patches may be physically disrupted or destroyed. In such highly dynamic systems it often is assumed that mobile fauna will be unresponsive to the arrangement of habitat patches or to other landscape attributes. The underlying logic is that faunal responses to landscape attributes will be masked by the spatial and temporal variability of such systems. In this proposal, we argue that mobile fauna in highly dynamic systems are, in fact, responsive to landscape attributes - especially patch arrangement. Population persistence and species interactions following the disruption of patches or changes in resources may be influenced greatly by the quality and arrangement of patches. In prior NSF-funded research, we found that stream-dwelling chironomids and copepods respond to the quality and distribution of habitat (leaf) patches in laboratory and field experiments, but we did not consider how patch stability, patch resource (leaf species) composition, or predator-prey interactions influence faunal dynamics. Here, we hypothesize that invertebrate abundance in streambeds is better explained at the scale of multiple patches (the "landscape") than at the scale of individual patches; is directly linked to the interactive effects of patch arrangement, patch stability, and patch quality; and, that invertebrate response to these three factors is modified by the presence of fish predators.We propose three field experiments to test the following specific hypotheses: (1) in stable landscapes (no patch movement), the abundance of stream invertebrates depends on patch arrangement and patch quality (leaf species composition); (2) when patches are not stable, the abundance of invertebrates depends on the interactive effects of patch arrangement and the level of patch stability; and (3) the response of stream invertebrates to patch arrangement, quality, & stability is influenced by the presence of predatory fish. To test the first two hypotheses, we will manipulate patch arrangement and patch stability or leaf quality using repeated measures factorial designs. For the third hypothesis, we will manipulate predator abundance and one landscape attribute at a time (patch arrangement, patch stability, or leaf quality). We will follow changes over time in the abundance of invertebrates at the level of landscapes, although we also will be able to assess variability within and among the individual patches that constitute each landscape.This work has important implications because we are asking if and how changes in landscapes --in terms of patch types and their arrangement and their resource levels -- influence biotic assemblages. Much of the current understanding of biotic responses to spatial landscape features is based primarily on theoretical and empirical work on systems in which the landscape features are fairly stable. Since many systems are highly dynamic -- patches move and patch quality varies temporally -- the type of research proposed here is greatly needed. As in our past grant, this research will be conducted as a collaborative effort between P. Silver at Penn State Erie, an undergraduate institution, and M.A. Palmer at University of Maryland College Park, a large research institution. The PI's, undergraduates, graduate students and a post doctoral associate will collaborate in all phases of the work, thereby providing maximum opportunity for students to participate in high quality research in an atmosphere of intense teamwork and collaboration with workers at a large research campus and a small primarily teaching campus.