1. Sources of Genetic Variation Factors increasing variation Mutation Migration Factors decreasing variation Natural selection Genetic drift in small populations (<1000)

2. Evidence of Selection in Natural Plant Populations

3. Selection Among Populations

4. The Common Garden Experiments of Clauson, Keck and Heiesy (1948)

5. Differences in phenotype across a gradient: Yarrow (Achiella spp) as an example

6. What is the source of variation? Different species – genetic variation? Same species – phenotypic plasticity?

7. Common Garden Experiment Stanford – 100’ Mather – 4600’ Timberline – 10,000’ Step #1: Obtain Plants from Source Populations

8. Source Plant Clones (e.g., piece of root) Location #1 Location #2 Step #2: Produce Clones Common Garden Experiment

9. Source Plant Clones (e.g., piece of root) Location #1 Location #2 Step #3: Plant clones in common gardens Common Garden Experiment Common Gardens Location #1 Location #2

10. Stanford Common Garden

11. Mather Common Garden

12. Timberline Common Garden

13. Interpretation of Results: Pure Plastic Response Source PlantClonesCommon Gardens Location #1 Location #2 ? Location #1 Location #2 ?

14. Interpretation of Results: Pure Genetic Response Source PlantClonesCommon Gardens Location #1 Location #2 Location #1 Location #2 ? ?

15. Experimental Outcome: Growth of Mather Achiella Clones Plastic responseGenetic response

16. Copyright © 1997-2001 by Jane Strong and Tom Chester http://tchester.org/sgm/conditions/blooms/idyellow.html A Second Example Potentilla glandulosa

17. Lowland Ecotype Lowland Plant ©Brother Alfred Brousseau, St. Mary's College

18. Montane Plant

19. Experimental Outcome: Growth of Potentilla Clones

20. Interpretation Part I Not a pure plastic response Not a pure genetic response What is the relationship between these organisms? Separate experiments show that crosses between different source populations produce viable offspring

21. Interpretation Part II These are not different species What then are they?

22. Ecotypes  the middle ground Genetically distinct organisms Phenotypically distinct in terms of Morphology Physiology Phenology Occur in distinct habitats Differences can be traced to ecological differences in home habitat Plants are potentially interfertile (i.e., same biologicial species)

23. An Interpretation Individuals or Ecotypes

24. Selection Within a Population

25. Purple loosestrife (Lythrum salicaria): an aggressive invasive species

26. Purple Loosestrife and Tristyly ♀  Pistal positions differ Three flower types (morphs) ♂  Anther positions differ Pollination patterns No self pollination Each morph can pollinate the other two morphs Less frequent morphs have higher fitness

27. Impact of Frequency-Dependent Selection on Invading Populations of Purple Loosestrife Study system with 24 newly invaded sites censused over a 5 year period Low evenness during year zero Evenness predicted to increase due to frequency dependent selection among morphs Prediction is met, indicating a change in population due to natural selection No change line (y=x)

28. Selection At a Global Scale

29. Convergent Evolution Example #1: Desert plants Euphorbiaceae: AfricaCactaceae: N. America Example #2: Alpine plants Campanulaceae: AfricaAsteraceae: S. America

30. Life Histories and Tradeoffs

31. Key Stages in the Life-History of a Plant Growth Flowering Pollination Seed Maturation Dispersal Dormancy Germination seed phase

32. The Ideal Plant Grow large rapidly Live forever Reproduce early and often

33. Life Histories and Tradeoffs

34. Impact of Limiting Resources

35. General Scheme of Resource Allocation Reproduction Pollen Nectar Ovules Seeds Growth Leaves Stems Roots Rhizomes Maintenance Structural support Storage Defenses Basal metabolism General order in which resources are used 123

36. General Scheme of Resource Allocation through time Time Available resource

37. Resource Allocation for a Typical Annual Plant Time

38. Resource Allocation over a typical year for a Stress Tolerating Plant Time

39. Tradeoffs and Limiting Resources vs