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

Bill Depth (mm)

Survival

From Benkman (2003) Evolution 57: 1176-1181.

1 = survived0 = died

Upper CI*

Best fit line

Lower CI*

* CI = confidence interval

Exhibit 3

From Benkman (2003) American Naturalist 162: 182-194.

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

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?”