Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, Florida, USA.
Department of Biological Science, Florida State University, Tallahassee, Florida, USA.
Ecology. 2018 Mar;99(3):652-660. doi: 10.1002/ecy.2128. Epub 2018 Jan 25.
The importance of predators in influencing community structure is a well-studied area of ecology. However, few studies test ecological hypotheses of predation in multi-predator microbial communities. The phytotelmic community found within the water-filled leaves of the pitcher plant, Sarracenia purpurea, exhibits a simple trophic structure that includes multiple protozoan predators and microbial prey. Using this system, we sought to determine whether different predators target distinct microorganisms, how interactions among protozoans affect resource (microorganism) use, and how predator diversity affects prey community diversity. In particular, we endeavored to determine if protozoa followed known ecological patterns such as keystone predation or generalist predation. For these experiments, replicate inquiline microbial communities were maintained for seven days with five protozoan species. Microbial community structure was determined by 16S rRNA gene amplicon sequencing (iTag) and analysis. Compared to the control (no protozoa), two ciliates followed patterns of keystone predation by increasing microbial evenness. In pairwise competition treatments with a generalist flagellate, prey communities resembled the microbial communities of the respective keystone predator in monoculture. The relative abundance of the most common bacterial Operational Taxonomic Unit (OTU) in our system decreased compared to the control in the presence of these ciliates. This OTU was 98% similar to a known chitin degrader and nitrate reducer, important functions for the microbial community and the plant host. Collectively, the data demonstrated that predator identity had a greater effect on prey diversity and composition than overall predator diversity.
捕食者在影响群落结构方面的重要性是生态学中一个研究得很好的领域。然而，很少有研究检验过捕食者在多捕食者微生物群落中的生态假设。猪笼草充满水的叶子中发现的植食性生物群落表现出一种简单的营养结构，其中包括多个原生动物捕食者和微生物猎物。利用这个系统，我们试图确定不同的捕食者是否针对不同的微生物，原生动物之间的相互作用如何影响资源（微生物）的利用，以及捕食者多样性如何影响猎物群落的多样性。特别是，我们努力确定原生动物是否遵循了已知的生态模式，如关键捕食或广义捕食。对于这些实验，用五种原生动物维持了 7 天的复制共栖微生物群落。通过 16S rRNA 基因扩增子测序（iTag）和分析来确定微生物群落结构。与对照（无原生动物）相比，两种纤毛虫通过增加微生物均匀度遵循了关键捕食者的模式。在与广义鞭毛原生动物的成对竞争处理中，猎物群落与单培养物中的相应关键捕食者的微生物群落相似。与对照相比，我们系统中最常见的细菌操作分类单元（OTU）的相对丰度在这些纤毛虫存在的情况下降低了。这个 OTU 与一种已知的几丁质降解菌和硝酸盐还原菌有 98%的相似性，这对微生物群落和植物宿主都很重要。总的来说，数据表明捕食者的身份对猎物的多样性和组成的影响大于捕食者的总体多样性。
