Evolution of Plants David Baum Game plan What are plants and how
did they evolve?
Differences between plant and animal evolution Some stories of
plant evolution 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
globes chemistry and ecology Early land plants were low to the
ground Over-time became larger, more complex, and acquired a
vascular system Multiple origins of trees
Crane and Leslie (2014) Why? An evolutionary arms 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) Competition for light (and other
resources) is a very important driver of plant evolution 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 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 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): Living gymnosperms have
unisexual cones
Are flowers monsters? Living gymnosperms have unisexual cones Seed
cone Pollen cone 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) If so:
quite successful!
~300,000 species of flowering plants Dominate all land ecosystems
(and several aquatic ones) Provide all food resources for humans
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 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), Why is polyploidy common in
plants?
Tolerance of different ploidy levels during development (dosage
compensation?) Often make unreduced gametes (rescues meiotic
problems) 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 Polyploidy
Whole Genome Duplications
Very many instances in land plant evolution All land plants are
ancient polyploids Plants have lots of extra genes 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 Pollination Stories
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 Pollen needs to
deliver the gametes to the egg cells
Stigma Pollen tubes grow through plant tissues navigated chemically
Pollen tubes grow through plant tissues navigated chemically 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) How do you think this evolved?
What else would you like to know? At the other extreme: Figs and
fig wasps
figs are tomb blossoms Implications There is a one-to-one
relationship between a fig species and its wasp pollinator species
Predicts cospeciation: that the figs and wasp 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 Actual result Host
switching Weiblen and Bush (2002) 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 Nio.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 Feel free to contact me:
[email protected]
Plant evolution is similar to other multicellular eukaryotes Arms
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: Twentieth Century Fox