2. Ch. 6: Evolutionary Processes/Outcomes

3. Plants and Environment
1) Liebig (1840)
Law of the Minimum: Growth/distribution depends on environmental factor most limiting
A Festive MoB CuMnZn Clapping Nicely

4. Plants and Environment
2) Shelford (American: early 1900s)
Upper limits for factors
Proposed “Theory of Tolerance”

5. Plants and Environment
Phenotype: appearance
Genotype: genetic make-up
Phenotype: determined by genotype & environment

6. Plants and the Environment
Equation:
Vp = Vg + Ve
Vp = total phenotypic variation
Vg = variation due to genotype
Ve = variation due to environment
Focus Vg

7. Plants and the Environment
Adaptation: What is an adaptation?

8. Plants and the Environment
Adaptation:
1) Genetically determined trait
2) With survival or reproductive benefit
How determine trait adaptation? Hard!
Genetic importance

9. Plants and the Environment
Genetic basis:
Heritability (h2): resemblance b/w relatives (shared genes)
h2 = Vg / Vp
Vg = variation due to genotype
Vp = total phenotypic variation

10. Plants and the Environment
1 approach: slope regression line (r2)
y = mx + b; m is slope
r2=0.52
r2=0
r2=1

11. Plants and the Environment
Plant height ex.
(r2)=0.21 or 21%
(h2)=0.21 or 21%
Fig. 6.3

12. Genetic Variation More better (generally) Why?
1) Raw material evolution
2) Dominant alleles mask “lethal recessives:”
Finish this sentence:
If you were haploid you’d be __________________

13. Genetic Variation Problem: genetic drift! Start: 50% mix 2 alleles
Small population (9 inds.)
Large population (50 inds.)

14. Genetic Variation
Ex, Wollemi “pine” (Australia)

15. Loss of Genetic Variability
Ex, Wollemi “Pine” (Australia)
Extinct 2 mya, 2 groups found plants!
Discoverer
David
Noble
Famous quote……

16. Loss of Genetic Variability
Ex, Wollemi “Pine” (Australia)
No measurable genetic diversity!
Collecting seeds
by helicopter

17. Genetic Variation Sources new genetic variation?
1) Mutation: Heritable change 2)

18. Plants and the Environment
Recall:
Adaptation:
1) Genetically determined trait
2) With survival or reproductive benefit
How show benefit? Hard! Ex

19. Adaptation Story
Homoblasty = same

20. Adaptation Story Homoblasty = Different = heteroblasty
Also called “juvenile” foliage
Ex, many Junipers (Juniperus)

21. Adaptation Story
Field trip: New Zealand!
20% trees heteroblastic

22. Adaptation Story Young plants (0-3 m tall) “divaricate” (
Older (> 3 m): normal
Pennantia corymbosa
normal
divaricate

23. Adaptation Story Adaptation climate? Adaptation herbivores (moas)?
normal
divaricate
Plagianthus regius
Moas?

24. New Zealand’s Moas Ratites (Order) 11 spp. Giant moa leg bones
Giant moa replica

25. New Zealand’s Moas
Hunted extinct by Maori

26. Adaptation Story
How study defense hypothesis?

27. Adaptation Story
Divaricate: 30-70%

28. Adaptation Story Non-native mammals not affected (shearing teeth)
Heteroblastic spp. declining

29. Plants and the Environment
Recall:
Adaptation:
1) Genetically determined trait
2) With survival or reproductive benefit
How show benefit? Hard!

30. Variation due to Environment
Vp = Vg + Ve

31. Variation due to Environment
Phenotypic plasticity: vary form/

32. Variation due to Environment
Ex, heterophylly: different leaf
(“hetero”=other; “phyll”=leaf)
Emergent vs.
Submerged leaves
Fig. 6.5

33. Species as ecological tool
Now: sp. as tool
Issues:
Sp. indicators environmental conditions?
Plants adapt at sp. level?
Revegetation/reforestation: does where we obtain plants matter?

34. Species Species def’n. Species: Populations Biological species
Others: cladistics, etc.

35. Species as ecological tool
Issues:
Sp. indicators environmental conditions?
Plants adapt at sp. level?
Revegetation/reforestation: does where we obtain plants matter?

36. Species
Good indicators: Ex, Quercus laevis (turkey oak).

37. Species Bad indicators: widespread & variable Differences
Vp = Vg + Ve
Bad indicators: widespread & variable
Differences
How evaluate?