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

在许多生态系统中，主要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破坏或破坏。在这种高度动态的系统中，人们通常认为流动的动物群对生境斑块的安排或其他景观属性没有反应。潜在的逻辑是，动物对景观属性的反应将被这些系统的时空变异性所掩盖。在这一建议中，我们认为，在高动态系统中，移动的动物实际上对景观属性（尤其是斑块排列）有响应。斑块破坏或资源变化后的种群持久性和物种相互作用可能受到斑块质量和排列的极大影响。在之前由nsf资助的研究中，我们在实验室和野外实验中发现，生活在河流中的摇尾虫和桡足类动物对栖息地（叶片）斑块的质量和分布做出了响应，但我们没有考虑斑块稳定性、斑块资源（叶片物种）组成或捕食者-猎物相互作用如何影响动物动态。在这里，我们假设河床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更好地解释；与斑块排列、斑块稳定性和斑块质量的相互作用直接相关；而且，无脊椎动物对这三个因素的反应被鱼类捕食者的存在所改变。我们提出了三个实地实验来验证以下具体假设：(1)在稳定景观（无斑块运动）中，河流无脊椎动物的丰度取决于斑块的排列和斑块的质量（叶片物种组成）；(2)当斑块不稳定时，无脊椎动物的丰度取决于斑块排列和斑块稳定程度的相互作用；(3)河流无脊椎动物对斑块排列、质量和稳定性的反应受到掠食性鱼类存在的影响。为了检验前两个假设，我们将使用重复测量因子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，我们将一次操纵捕食者丰度和一个景观属性（斑块排列、斑块稳定性或叶片质量）。我们将在景观水平上跟踪无脊椎动物丰度随时间的变化，尽管我们也将能够评估构成每个景观的单个斑块内部和之间的可变性。这项工作具有重要的意义，因为我们正在询问景观的变化-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的响应的理解主要是基于对景观特征相当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——补丁移动和补丁质量随时间变化——这里提出的研究类型是非常必要的。与我们过去的拨款一样，这项研究将由宾夕法尼亚州立大学伊利分校的P. Silver（本科机构）和马里兰大学帕克分校的M.A. Palmer（大型研究机构）合作进行。PI，本科生，研究生和博士后助理将在工作的各个阶段进行合作，从而为学生提供最大的机会，在一个大型研究校园和一个小型主要教学校园的强烈团队合作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.