1. Evolution of Plants David Baum

2. Game plan What are “plants” and how did they evolve?
Differences between plant and animal evolution
Some stories of plant evolution

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
*Profoundly affecting the globe’s chemistry and ecology

4. Early land plants were low to the ground

5. Over-time became larger, more complex, and acquired a vascular system

7. Multiple origins of “trees”
Crane and Leslie (2014)

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 (and other resources) 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..
Greater diversity in sexual systems
Abundant asexuality
Self-incompatibility
Sexual system diversity

13. 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)

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

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

16. 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

17. 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)

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

19. 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
Salix (Willow)

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

21. 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:

22. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
Greater diversity in sexual systems
More chemistry less behavior
Opium Poppy
Hops
Coffee
Natural rubber

23. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
Greater diversity in sexual systems
More chemistry less behavior
Polyploidy more common
Chester et al Genes 1(2),

24. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
Greater diversity in sexual systems
More chemistry less behavior
Polyploidy more common
More evolution by “hopeful monsters” (maybe)

25. 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):

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

27. 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)

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

29. Pollination Stories

30. Pollination Pollination is transfer of pollen from anthers to stigma
Pollination ≠ fertilization
Necessary to make seeds
critical for reproduction
important for agriculture
Apple

31. 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

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

33. Pollen tubes grow through plant tissues – navigated chemically

34. Pollen tubes grow through plant tissues – navigated chemically

35. Plants have evolved diverse ways to get pollen from one flower to another
Wind
Water (rare)
Animals
Mutualistic (give a reward)
Parasitic (trick the animal)

36. Feel free to contact me: dbaum@wisc.edu
Plant evolution is similar to other multicellular eukaryotes
But they are a great model for studying evolution (e.g., the evolution of sex)
Coevolution with animals for pollination (and dispersal) is important
Botany is cool
Feel free to contact me: