Coevolution
Laura Conner, Susan Hester, Anne-Marie Hoskinson, Mary Beth Leigh, Andy
Martin, Tom Powers
• Context: LD evolution or ecology, 30-150
students
• Foundational knowledge: mechanisms of
natural selection, adaptations, two-species
interactions
• Preparation: definition of coevolution
Unit learning goals:
• Understand that species interact on an
evolutionary time scale
• Know that other organisms can be powerful
agents of selection
Unit learning outcomes:
1. Define coevolution.
2. Identify types of evidence that would help
determine whether two species are currently in
a coevolutionary relationship.
3. Interpret and draw graphs.
4. Evaluate evidence about whether two species
are coevolving.
5. Make testable predictions based on the
hypothesis that two species are coevolving.
6. Predict the outcome of a perturbation to a
coevolved system.
Teachable tidbit learning outcome:
1. Define coevolution.
2. Identify the evidence that would help determine
whether two species are currently in a
coevolutionary relationship.
3. Interpret and draw graphs.
4. Evaluate evidence about whether two species
are coevolving.
5. Make testable predictions based on the
hypothesis that two species are coevolving.
6. Predict the outcome of a perturbation to a
coevolved system.
Coevolution requires…
• Geographic overlap
• Reciprocal effects on traits
How is this coevolution?
What happens to the gazelles when the cheetahs
get faster?
http://www.arkive.org/cheetah/acinonyx-jubatus/video-08c.html
The Plot:
In the Rocky Mountains, red squirrels and crossbills both eat
lodgepole pine seeds. In some locations, squirrels are absent.
The species interact when they occur in the same place … but
do they have reciprocal effects on one another’s traits?
Red squirrels
Crossbill birds
Lodgepole pine cone
After http://evolution.berkeley.edu/evosite/evo101/IIIF1Casestudyofcoevo.shtml)
Exhibit 1
From Benkman (2001) Evolution 55: 282-294.
Exhibit 2
Upper
CI*
Survival
Best fit
line
1 = survived
0 = died
Lower
CI*
Bill Depth (mm)
From Benkman (2003) Evolution 57: 1176-1181.
* CI = 95% confidence interval
Value
9
8.8
8.6
8.4
8.2
8
7.8
7.6
7.4
7.2
7
Exhibit 3
Before crossbill
predation
After crossbill
predation
Cone Shape
(width/length*15)
Cone Mass (grams)
Pine Cone Trait
From Benkman (2003) American Naturalist 162: 182-194.
Image credits:
http://kuro-risu.blogspot.com/2010/03/american-red-squirrel.html
http://www.learner.org/jnorth/tm/spring/GeneralistSpecialistDiscussion.html
http://wormtracks.wordpress.com/2012/01/05/tree-of-the-month-lodgepole-pine/
Based on the data presented,
____________________ are in a
coevolutionary relationship.
(a) squirrels and pinecones
(b) crossbills and pinecones
(c) squirrels and crossbills
(d) (a) and (b)
(e) none of these species
What kind of additional evidence
would indicate a coevolutionary
relationship between squirrel traits
and pinecones?
Make a prediction based on the hypothesis that
pines are driving evolution of squirrel jaws.
From Smith 1970. Ecological Monographs 40: 349-371
Exhibit 4
From Smith 1970. Ecological Monographs 40: 349-371
Learning Objective
Active learning
Assessment
Diversity
Evaluate evidence
about whether two
species are
coevolving.
• Case study
• Group
processing
• Figure
interpretation
• Relationship
map
Formative:
• Group processing
about
presence/direction
of interaction
• Clicker question
• Video clip
• Individual and
group learning
• Verbal, graphical,
tactile
information
Summative:
“Here are data for
two species. Are
they coevolving, or
not? Why?”