1. Evolution of Plants David Baum

2. Game plan What are “plants” and how did they evolve?
Differences between plant and animal evolution
Why were angiosperms so successful?
Pollination biology

3. What are the three most important
What are the three most important* events in the evolution of life on earth?
Oxygenic photosynthesis (cyanobacteria)
Invasion of land (plants)
Human agriculture and technology (plants and humans)
*Profoundly affecting the globe’s chemistry and ecology

4. Early land plants were low to the ground

5. They became larger, more complex, and acquired a vascular system
Time

7. Multiple origins of “trees”
Crane and Leslie (2013)

8. Why?

9. An evolutionary arm’s race
The Red Queen principle
Now, here, I see it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that! (Through the Looking Glass, Lewis Carroll)

10. Competition for light is a very important driver of plant evolution

11. Problems that plants faced
Gain light, water, nutrients
Escaping predators (once animals invaded land)
Sex!
If you want to know more:
Botany 130, 300, 305, 401, 500
Fern sperm cell

12. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
More abundant polyploidy and allopolyploid speciation

13. Why is polyploidy common in plants?
Tolerance of different ploidy levels during development (dosage compensation?)
Often make unreduced gametes (“rescues” meiotic problems)
Or?
Chester et al Genes 1(2),

14. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
More abundant polyploidy and allopolyploid speciation
Greater diversity in sexual systems

15. Terminology (from Wikipedia)

16. Self-pollination is important in some species
Reproductive assurance
Viola (Some flowers self in bud)
Arabidopsis (pollen shed onto stigma)
Hibiscus (active selfing; Ruan et al. 2010)

17. Some species produce seeds asexually
May still require (self) pollen
Dandelion - Taraxacum
Blackberry- Rubus

18. Mechanisms that promote cross-pollination
Spatial separation of anthers and stigma in a flower
Wild buckwheat

19. Mechanisms that promote cross-pollination
Spatial separation of anthers and stigma in a flower
Temporal separation of pollen release and stigma receptivity
Female phase
Male phase
Aeonium

20. Mechanisms that promote cross-pollination
Spatial separation of anthers and stigma in a flower
Temporal separation of pollen release and stigma receptivity
Self-incompatibility (SI)

21. Mechanisms that promote cross-pollination
Spatial separation of anthers and stigma in a flower
Temporal separation of pollen release and stigma receptivity
Self-incompatibility
Tsuchimatsu et al. (2010) Nature
Self pollen
Cross pollen

22. Consequences SI taxa speciate slower than SC taxa
But they also go extinct slower
SI has higher net rate of diversification
Emma E. Goldberg et al. Science 2010;330:

23. Mechanisms that promote cross-pollination
Spatial separation of anthers and stigma in a flower
Temporal separation of pollen release and stigma receptivity
Self-incompatibility
Dioecy ( origins!)
Varied mechanisms/genetics
Salix (Willow)

24. Actually it is more complicated
Gynodioecy: Females + hermaphrodites
Androdioecy: Males (top) + hermaphrodites
Wild strawberry
Datisca

25. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
More abundant polyploidy and allopolyploid speciation
Greater diversity in sexual systems
More chemistry less behavior

26. Are there differences between plant and animal evolution?
Amazing diversity of chemicals produced
Still evolving
Be thankful!
Opium Poppy
Hops
Natural rubber
Coffee

27. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
More abundant polyploidy and allopolyploid speciation
Greater diversity in sexual systems
More chemistry less behavior
Maybe more evolution by “hopeful monsters”

28. Examples of “hopeful monsters?”
Rudall PJ, Bateman RM
Rudall PJ, Bateman RM
Trends Plant Sci. 8(2):76-82.
Biol Rev Camb Philos Soc.77(3):

29. Living gymnosperms have unisexual cones
Are flowers monsters?
Living gymnosperms have unisexual cones
Seed cone
Pollen cone

30. Are flowers monsters? A flower is a bisexual “cone”
Megasporophyll
Microsporophyll
(stamen)
A flower is a bisexual “cone”
(although unisexual flowers have evolved in many groups)

31. If so: quite successful!
~300,000 species of flowering plants
Dominate all land ecosystems (and several aquatic ones)
Provide all food resources for human
Why so successful?

32. Why are the angiosperms so successful?
Better competitors?
Reticulate venation (better in low light)
Vessels (grow faster in moist environments)
Reduced gametophytes and double fertilization (more rapid seed formation)

33. Why are the angiosperms so successful?
Elevated speciation rate
Animal pollination (sister lineages become reproductively isolated quickly)
Fruit (allows for long distance dispersal)
Reduced extinction rate
Animal pollination allows for persistence at low densities

34. Animal pollination

35. Pollination (only occurs in seed plants) avoids the need for motile sperm
Pollen is a minute male plant
Can be carried by wind (rarely water)
More commonly animals do it
Insects
Birds
Mammals

36. Pollen needs to deliver the gametes to the egg cells
Stigma

37. Plants have evolved diverse ways to get animals to visit
Mentzelia involucrata
Mutualistic (give a reward)
Nectar
Pollen
Solid food
Perfume
Heat
Sex
Parasitic (trick the animal)
Mohavea confertiflora

39. How do you think this evolved?
What else would you like to know?

40. At the other extreme: Figs and fig wasps
figs are “tomb blossoms”

42. Implications
There is a one-to-one relationship between a fig species and its wasp pollinator species
Predicts cospeciation: that the figs and wasp

43. Prediction: One-to-one species association Cospeciation A a C c B b D
Wasp phylogeny
Fig phylogeny C c B b D d E e F f

44. Actual result
Host switching
Weiblen and Bush (2002)

45. Feel free to contact me: dbaum@wisc.edu
Plant evolution is similar to other multicellular eukaryotes
Arm’s race for light
Plants (may) differ in frequency of polyploidy, chemical evolution, sexual lability, hopeful monsters
Angiosperms very successful
Coevolution with animals for pollination
Feel free to contact me: