Parasites – They’re what’s for dinner: Investigating the role of parasites in aquatic food webs

Field sampling for amphibians and aquatic invertebrates. (Photo courtesy of Clara Boland)


Sarah A. Orlofske

University of Wisconsin - Stevens Point (


How does the presence of parasites influence characteristics of freshwater food webs?


Food web ecology, wetland communities, parasitism, disease ecology, complex life cycles, network modeling


Students will:

  • evaluate the methodology for collecting and analyzing food web data
  • investigate metadata provided with a well-resolved food web database including parasites
  • explore parasite life cycles and interactions with other species in a food web context
  • formulate research questions and propose hypotheses about how including parasites could influence properties of the entire food web as well as individual taxa
  • manipulate the food web data set to extract the relevant data, calculate food web metrics, and create figures that illustrate the results
  • discuss their findings and relate it back to key ecological concepts


  • Hypothesis formation: Generate questions and propose hypotheses about how the inclusion of infectious agents may affect properties of aquatic food webs and individual taxa in those communities.
  • Data management: Evaluate metadata connecting raw data and mathematical representations of feeding relationships to relevant ecological information.
  • Data analysis: Organize and summarize spreadsheet data in MSExcel and calculate standard food web metrics using MSExcel or R
  • Data visualization: Create and annotate figures of the data.
  • Data interpretation: Interpret results and connect to ecological principles of food webs.


Guided inquiry, open-ended inquiry, predict-observe-explain, small group discussion, computer-based projects, calculation


Food web diagram and interpretation of hypotheses, tables and figures from spreadsheet data, written answers to questions.


Preston, D.L., Orlofske, S.A., McLaughlin, J.P, Johnson, P.T.J. 2012. Food web including infectious agents for a California freshwater pond. Ecology 93:1760. Ecological Archives E093-153.


  • Full Article Text [docx], [pdf]

  • Description of Excel Files:

    • Quick_Pond_Nodes – dataset that provides background information on all of the taxa and/or life stages included in the food web. Note: blank cells indicate that information was not collected or is not applicable.
    • Quick_Pond_Links – dataset that provides the information on trophic interactions using a two column format where consumers and resources are indicated as well as the type of evidence for that interaction and the source (if any).

    Supporting files

    • Quick_Table_2A & Quick_Table_2B – Provides the metadata for the Quick_Pond_Nodes data set including the definitions and descriptions of each of the column headers (2A) and variables (2B)
    • Quick_Table_3A, Quick_Table_3B, & Quick_Table_3C – Provides the metadata for the Quick_Pond_Links data set including the definitions and descriptions of each of the column headers (3A) and variables (3B) and link types (3C).
    • Quick_Table_4 – Provides the metadata for the missing, under-represented groups and severely aggregated nodes for food web dataset.
    • Quick_Pond_Nodes_Key - This spreadsheet provides some of the basic food web metrics for taxa in the Quick Pond Dataset that can be used in exploring the relationships among parasites and free-living species in the community.
    • Quick_Pond_Links_Key - This spreadsheet represents a simpler version of the more detailed Links spreadsheet and is suitable for use with the provided Food web dataset R script found below.
    • Foodweb dataset R script - This is an example R script that can be used by instructors, students, or both for the completion of the data analysis portion of the data set activities. It includes executable examples and detailed descriptions.


    This data set was developed through the DIG into Data Faculty Mentoring Network through QUBES (Quantitative Undergraduate Biology Education and Synthesis) and I would like to thank all the members of that group for insightful discussions, useful resources, and helpful feedback. I would also like to thank Daniel L. Preston for support of this data set and access to file formats that assisted in adapting the dataset for classroom use. I would like to thank Robert C. Jadin for helpful feedback during each stage of the process.


    Sarah A. Orlofske. March 2018, posting date. Parasites – They’re what’s for dinner: Investigating the role of parasites in aquatic food websTeaching Issues and Experiments in Ecology, Vol. 13: Practice #3 [online].