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
More chemistry less behavior
Maybe more evolution by “hopeful monsters”

13. 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):

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

15. 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)

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

17. Are there differences between plant and animal evolution?
Very few – plants are excellent “model systems”
But..
Greater diversity in sexual systems
Abundant asexuality
More chemistry less behavior
Maybe more evolution by “hopeful monsters”
Polyploidy

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

19. Why is polyploidy common in plants?
Tolerance of different ploidy levels during development (dosage compensation?)
Often make unreduced gametes (“rescues” meiotic problems)

20. Why is polyploidy common in plants?
Tolerance of different ploidy levels during development (dosage compensation?)
Often make unreduced gametes (“rescues” meiotic problems)
Many crops are polyploid
wheat and potato

21. Polyploidy – Whole Genome Duplications
Very many instances in land plant evolution
All land plants are ancient polyploids
Plants have lots of “extra” genes

22. Polyploidy – Whole Genome Duplications
Very many instances in land plant evolution
All land plants are ancient polyploids
Plants have lots of “extra” genes
Sometimes polyploidy is associated with speciation
Allopolyploidy
Hybrid speciation
D. Soltis and P. Soltis: Am. J. Bot

23. Pollination Stories

24. 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

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

26. Pollen tubes grow through plant tissues – navigated chemically

27. Pollen tubes grow through plant tissues – navigated chemically

29. 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)

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

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

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

35. 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

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

37. Desert Ecology and Evolutionary Biology
Botany 575 • Tom Givnish and Kate McCulloh
Weekly meetings in Spring 2016 / field trip March 19 – 27, 2016
Deserts are extreme environments that support an unexpected diversity of plant species and adaptations. An historic opportunity to study speciation and photosynthetic/hydraulic adaptations in desert plants, especially winter annuals, is likely this year due to a massive
El Niño. We will visit a wide range of desert habitats and conduct research during a 8-day field trip to southern California this spring, complemented by lab work and writing papers for publication. • Open to undergrads and grad students • Meets 1:00 – 2:15 W • Costs ca. $675/student • Applications due December 1 –

38. Feel free to contact me: dbaum@wisc.edu
Plant evolution is similar to other multicellular eukaryotes
Arm’s race for light
Polyploidy is especially important
Coevolution with animals for pollination (and dispersal) is important
Botany is REALLY important
Feel free to contact me:

39. Twentieth Century Fox