Skip to Content

Speciation and the Threespine Stickleback


Author(s)

Joan Sharp
Department of Biological Sciences
Simon Fraser University
jsharp@sfu.ca
Erin Barley
Department of Biological Sciences
Simon Fraser University
ebarley@sfu.ca
Kevin K.-W. Lam
Department of Biological Sciences
Simon Fraser University
klamf@sfu.ca
Suraaj Aulakh

Simon Fraser University
suraaj_aulakh@sfu.ca
Allison Cornell
Department of Biological Sciences
Cedar Crest College
Allison.Cornell@cedarcrest.edu
Kathleen A. Fitzpatrick
Department of Biological Sciences
Simon Fraser University
kathleef@sfu.ca

Abstract

This case study teaches students about allopatric speciation through an investigation of the benthic and limnetic sticklebacks of Paxton Lake, which are among the youngest species on Earth, diverging from each other after the Pleistocene glaciers melted and the Gulf Islands formed. Researchers at the University of British Columbia have carried out a variety of fascinating studies on these hardy little fish. Results from this research (formatted as data sheets included in the teaching notes) are provided to students who design experiments and then compare actual data to investigate why benthic and limnetic sticklebacks seldom interbreed in Paxton Lake. Developed for a first-year biology course for majors organized around the general theme of evolution and the history of life on Earth, this case study is an updated version of another case in the collection, “Something’s Fishy in Paxton Lake” (Sharp, 2001). The current version is especially suited for a flipped classroom in which students prepare for class ahead of time with a reading assignment that also involves the viewing of a video by the case authors that introduces the mechanisms of allopatric speciation.


Objectives

  • Apply the mechanisms of allopatric speciation to a real life situation.
  • Explain how natural selection may act to favor divergent morphologies as incipient species adapt to different ecological roles.
  • Explain how natural selection acts to favor the evolution of reproductive isolating mechanisms.
  • Design experiments to test hypotheses about speciation.
  • Interpret data and understand how they may be used to support or reject hypotheses.
  • Discuss the status of benthic and limnetic stickleback fish as distinct species, with reference to different species concepts (biological, morphological, ecological).

Keywords

Allopatric speciation; species; founder effect; genetic drift; mutation; natural selection; character displacement; dispersal; vicariance; stickleback; Gasterosteus aculeatus; lake zonation; causation; assortative mating; predation risk; foraging success

Topical Areas

N/A

Educational Level

Undergraduate lower division

Format

PDF

Type / Methods

Discussion, Flipped, Interrupted

Language

English

Subject Headings

Biology (General)  |   Evolutionary Biology  |   Wildlife Management  |   Zoology  |  


Date Posted

1/3/2019

Teaching Notes

Case teaching notes are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.

Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

Answer Key

Answer keys for the cases in our collection are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.

Videos

The following video(s) are recommended for use in association with this case study.

Comments