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S1. Coevolution or not? Crossbills, Squirrels, and Pinecones Anne-Marie Hoskinson, Laura Conner, Susan Hester, Mary Beth Leigh, Andrew P. Martin, Tom Powers.

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Presentation on theme: "S1. Coevolution or not? Crossbills, Squirrels, and Pinecones Anne-Marie Hoskinson, Laura Conner, Susan Hester, Mary Beth Leigh, Andrew P. Martin, Tom Powers."— Presentation transcript:

1 S1. Coevolution or not? Crossbills, Squirrels, and Pinecones Anne-Marie Hoskinson, Laura Conner, Susan Hester, Mary Beth Leigh, Andrew P. Martin, Tom Powers 1

2 What are the conditions for coevolution? think – pair – share 2

3 Necessary conditions 1)Two or more interacting species exist in the same place and at the same time 3

4 Necessary conditions 1)Two or more interacting species exist in the same place and at the same time AND 2) Each species affects the other species’: A.survival B.reproduction (fitness) OR C.some other allele that affects A or B 4

5 Coevolution requires… BOTH Geographic overlap of populations Reciprocal effects on traits 5

6 How is this coevolution? What happens to the gazelles when the cheetahs get faster?

7 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 cones After Image credits (L to R): 7

8 Lodgepole Pine Larger, open, fewer seeds Smaller, closed, more seeds 8 Figure 1, Benkman et al Evolution 55: adapted from Figure 2, Benkman et al Am. Nat. 162: lberta.ca/lan ds- forests/trees - plants/trees/ images/GFX- Lodgepole- Pine-01.jpg aft.blogspot.com/2012/12/ro cky-mountain-tree- identification.html

9 Crossbills Complete overlap with pine trees 9 Watch how crossbills manipulate seeds to feed: Variation in crossover direction and beak depth (length) images/crossbills_1.jpg shorter, right crossover longer, left crossover

10 Red squirrels Pines + crossbills, but no squirrels until 1950 Watch a red squirrel manipulate a cone to feed: 10 squirrel/tamiasciurus-hudsonicus/video- 02a.html rus_hudsonicus_CT.jpg

11 What You Will Do Small groups of 4 Each group gets one Exhibit (numbered 1 – 3) Work with:  Modeling Evolutionary Relationships  System Map  your team’s Exhibit  each other in order to make a claim, backed by evidence (your Exhibit) about what’s happening 10 minutes 11

12 12

13 Exhibit 1. From Benkman (2001) Evolution 55:

14 Exhibit 2. Bill Depth (mm) Survival From Benkman (2003) Evolution 57: = survived 0 = died Upper CI* Best fit line Lower CI* * CI = 95% confidence interval 14

15 Exhibit 3. From Benkman (2003) American Naturalist 162:

16 The three species 16 risu.blogspot.com /2010/03/america n-red- squirrel.html Squirrel photo orth/images/graphics/a- b/Beak-Crossbill.jpg Crossbill bill photo mo/naturescience/image s/lodgepole_pine.jpg Lodgepole pine cone photo

17 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

18 What kind of additional evidence would indicate a coevolutionary relationship between squirrel traits and pinecones?

19 Exhibit 4. From Smith Ecological Monographs 40:

20 Sketching predictive graphs 20 When [independent variable] changes in pine cones… …[Dependent variable] in squirrels will change as a result.


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