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Caught in the Act:Caught in the Act:Agents of Evolutionary ChangeAgents of Evolutionary Change

Peter B. Woodruff

Biology Department

Champlain-St. Lambertwoodruf@champlaincollege.qc.ca

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Caught in the Act: Overview

• What should we know already?– Measuring microevolution (Hardy-Weinberg)– 5 agents of evolutionary change

• How might we rank these agents?– In general– In specific cases

• What might an “evolution experiment” look like?

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow– Migration

• Nonrandom Mating

• Genetic Drift

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow– Migration– Hybridization

• Nonrandom Mating

• Genetic Drift

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift– Founder effect

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift– Founder effect– Bottleneck effect

• Selection

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift

• Selection– Artificial

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Agents of Evolutionary Change

• Mutation

• Gene Flow

• Nonrandom Mating

• Genetic Drift

• Selection– Artificial– Natural

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Ranking Agents of Evolutionary Change

• How would we rank these agents?

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Ranking Agents of Evolutionary Change

• How would we rank these agents? HandoutAgents of Evolutionary Change

Rank according to their relative impact on evolution for each population size:

(Where 1 is the greatest and 5 is the least contribution)Mutation

large population small population1 2 3 4 5 1 2 3 4 5

Gene Flowlarge population small population

1 2 3 4 5 1 2 3 4 5Nonrandom Mating

large population small population1 2 3 4 5 1 2 3 4 5

Genetic Drift large population small population

1 2 3 4 5 1 2 3 4 5Selection

large population small population1 2 3 4 5 1 2 3 4 5

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?– Theoretical models

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?– Theoretical models– Experiments

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?– Theoretical models– Experiments

• Laboratory

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?– Theoretical models– Experiments

• Laboratory

• Field

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?– Theoretical models– Experiments

• Laboratory• Field• “Natural”

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Ranking Agents

• How would we rank these agents?– What criteria should we choose?

• How might we actually determine their relative contribution to evolution?– Theoretical models– Experiments

• Laboratory• Field• “Natural” e.g.: cline, introduced species

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©George Gilchrist

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Worldwide range of Drosophila subobscura circa 1960, Modified, with permission from: Rodríguez-Trelles, F., et al., Conservation Ecology 2(2):2 http://www.consecol.org/vol2/iss2/art2.

Latitude

Longitude 0o

0o

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The latitudinal cline in wing size of European D. subobscura, excerpted and modified with permission from Huey, R.B., et al, Science 287:308-9, Copyright © 2000 by The American Association for the Advancement of Science.

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Worldwide range of Drosophila subobscura. Originally an Old-World species, it has recently colonized North and South America. Excerpted with permission from: Rodríguez-Trelles, F., et al., Conservation Ecology 2(2):2 http://www.consecol.org/vol2/iss2/art2.

Latitude

55o N

35o N

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What is the “Natural Experiment?”1. Studies reveal that Old World Drosophila

subobscura form a latitudinal cline in body size.

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What is the “Natural Experiment?”1. Studies reveal that Old World Drosophila

subobscura form a latitudinal cline in body size.

2. D. subobscura was introduced into the western Americas about 20 years ago & is now widespread.

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What is the “Natural Experiment?”1. Studies reveal that Old World Drosophila

subobscura form a latitudinal cline in body size.

2. D. subobscura was introduced into the western Americas about 20 years ago & is now widespread.

3. Sampling after ten years showed no American cline.

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What is the “Natural Experiment?”1. Studies reveal that Old World Drosophila

subobscura form a latitudinal cline in body size.

2. D. subobscura was introduced into the western Americas about 20 years ago & is now widespread.

3. Sampling after ten years showed no American cline.

4. Samples taken after twenty years are now available.

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What is the “Natural Experiment?”1. Studies reveal that Old World Drosophila

subobscura form a latitudinal cline in body size.

2. D. subobscura was introduced into the western Americas about 20 years ago & is now widespread.

3. Sampling after ten years showed no American cline.

4. Samples taken after twenty years are now available.

5. What hypotheses could be tested using these data?

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Measuring Fly Wing SizeStandard operating Procedure

1. For each group: select a measurer, recorder and data entry specialist.

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Measuring Fly Wing SizeStandard operating Procedure

2. For each wing: (please do not mark on sheets)

measure the distance between arrows, in cm.

Vein L4

Flybase figure used with permission; site:

http://flybase.bio.indiana.edu/

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Measuring Fly Wing SizeStandard operating Procedure

3. Record each measurement on the data table provided, to the nearest tenth of a centimeter.

4. Transfer your data to the computer spreadsheet.

5. Predict the latitudinal position of your samples.

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z The latitudinal cline in wing size of introduced North American D. subobscura is converging on that for native [European (EU)] flies. Female wing length of introduced North American flies increases with latitude. Excerpted with permission from Huey et al, Science 287, 308-309. Copyright © 2000 by The American Association for the Advancement of Science.

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The relative length of the basal portion of vein IV versus latitude for D. subobscura (only the females are graphed; the pattern for males is similar). Thus, the wing section controlling the cline in wing length differs between North American and European populations. Excerpted with permission from Huey et al, Science 287, Number 5451, p. 308. Copyright

© 2000 by The American Association for the Advancement of Science.

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What can we learn from our evolution “experiment”?

• About experimental design

• About evolution in action.

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Acknowledgements

I would like to give special thanks to George Gilchrist, Chairman, Biology Department, Clarkson University, for his personal insights into his work on Drosophila subobscura (and his photograph of European flies), and to those participants, many of them my students at Champlain-St.Lambert, who improved this activity through their comments. Any errors are mine alone.

PBW, Jan. 2001

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References

• Original research and graphs from R.B. Huey, G.W. Gilchrist, M.L.Carlson, D.Berrigan, & L. Serra, “Rapid Evolution of a Geographical Cline in an Introduced Fly”, Science 287 (5451)(14 Jan 2000):pp.308-309, used with permission.

• Wing drawing from Flybase www site, originally in Bryant, P.J., Pattern formation in imaginal discs. Ashburner, Wright, 1978-1980 1978 c:230-335, used with permission.

• World distribution of Drosophila subobscura map from Francisco Rodríguez-Trelles, Miguel A. Rodríguez, and Samuel M. Scheiner, Tracking the genetic effects of global warming: Drosophila and other model systems, Conservation Ecology 2(2):2 http://www.consecol.org/vol2/iss2/art2, used with permission.

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See also:Balanya, J; Segarra, C; Prevosti, A; Serra, L. (1994) Colonization of America by Drosophila subobscura: The founder event and a rapid expansion. Journal of Heredity, 85, n.6, 427-432.

Prevosti, A., G. Ribó, L. Serra, M. Aguadé, J. Balaña, M. Monclús, and F. Mestres. (1988) Colonization of America by Drosophila subobscura: experiment in natural populations that supports the adaptive role of chromosomal-inversion polymorphism. Proceedings of the National Academy of Sciences (USA) 85:5597-5600.

Misra, R. K., and E. C. R. Reeve. (1964) Clines in body dimensions in populations of Drosophila subobscura.

Genetical Research 5:240-254.

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And of course:

Weiner, Jonathan (1995), The Beak of the Finch: A Story of Evolution in Our Time, Vintage, New York.