Effects of multiple invasive species in experimental aquatic communities

Two common wetland invasive species, American bullfrog (Lithobates catesbeianus) and mosquitofish (Gambusia affinis and G. holbrooki), that were caught with a seine from a California pond. Photo credit: Jeremy Monroe/Freshwaters Illustrated.


Miranda D. Redmond1,4, Daniel L. Preston1, and Rowan M. Gaffney2,3

1Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309

2Department of Geological Sciences and Engineering, University of Nevada, Reno, NV 89557

3Itasca Denver, Lakewood, CO 80228

4Corresponding Author: Miranda D. Redmond (


What are the effects of two invasive species, western mosquitofish (Gambusia affinis) and the American bullfrog (Lithobates catesbeianus), on a native aquatic community?


Invasion ecology, wetland communities, amphibian decline, direct and indirect effects, trophic cascades


This exercise is designed for upper division biology and environmental science students and could be especially useful for students in a data management, data analysis, or wetland ecology course. In this exercise, students first work in small groups to collect background information on what mosquitofish and bullfrogs consume and then modify a food web based on that knowledge. Students then develop hypotheses of how these two invasive species may affect native amphibian species, snails, and zooplankton. Following, students work individually to analyze experimental mesocosm data to determine the effects of the two invasive species on native aquatic taxa (amphibians, snails, zooplankton, and phytoplankton). Afterwards, students discuss their findings and modify their food web based on the results.


  • Hypotheses formation: Develop testable hypotheses and create a conceptual diagram
  • Data management and analysis: Summarize data in excel or a relational database to create tables and graphs
  • Data visualization: Create figures to visually represent the data
  • Data interpretation: Interpret results and draw a hypothesized food web based on the data
  • Collaboration: Effectively collaborate with classmates to develop hypotheses and interpret findings


Computer-based projects, calculation, problem-based learning, cooperative learning, critical thinking


Food web diagram and hypotheses, database or summarized excel files, figures and answers to questions


Preston, D.L., J.S. Henderson, and P.T.J. Johnson 2012. Community ecology of invasions: direct and indirect effects of multiple invasive species on aquatic communities. Ecology 93: 1254–1261.


  • Full Article Text [doc], [pdf]

  • Description of Additional Files:

    • Student_Excel – this excel file contains all of the data needed to complete the core activity: [xlsx]
    • Instructor_Excel – this excel file contains all of the data as well as the accompanying graphs to answer the questions posed in the core activity: [xlsx]
    • Student_Excel_All_Data – this excel file contains additional data from the mesocosm experiment to answer the optional extension tasks: [xlsx]
    • Instructor_MS_Access_Database – this Microsoft Access database contains all of the data and the queries necessary to answer the questions in the core activity. This database can therefore serve as a useful answer key for classes in which students are expected to build a MS Access database. [accdb]
    • Instructor_PostgreSQL_code - this code provides all of the structured query language (SQL) code necessary to answer the questions in the core activity using a PostgreSQL database. This code is annotated so that the purpose of each line of code is clear. This code can therefore serve as a useful answer key for classes in which students are expected to summarize their data in a postgreSQL database. [sql]
    • Instructor_Powerpoint – this PowerPoint is designed for instructors to present to the students and is divided into two sections (Part I and Part II). Part I provides background on the experiment and dataset. This part should be presented at the beginning of the lesson. Part II of the PowerPoint shows figures and results that should be shown after the students have completed the activity. The PowerPoint file includes associated notes for each slide, such as background information on the methods, explanations of the results, and discussion prompts. [ppt]


    Miranda D. Redmond, Daniel L. Preston, and Rowan M. Gaffney. August 2014, posting date. Effects of multiple invasive species in experimental aquatic communitiesTeaching Issues and Experiments in Ecology, Vol. 10: Practice #2 [online].