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Ch. 6: Evolutionary Processes/Outcomes
Plants and Environment
• 1) Liebig (1840)
– Law of the Minimum: Growth/distribution
depends on environmental factor most limiting
A Festive MoB CuMnZn Clapping Nicely
Plants and Environment
• 2) Shelford (American:
early 1900s)
– Upper limits for factors
– Proposed “Theory of
Tolerance”
Plants and Environment
• Phenotype: appearance
• Genotype: genetic make-up
• Phenotype: determined by genotype &
environment
Plants and the Environment
• Equation:
• Vp = Vg + Ve
• Vp = total phenotypic variation
• Vg = variation due to genotype
• Ve = variation due to environment
Focus Vg
Plants and the Environment
• Adaptation: What is an adaptation?
Plants and the Environment
• Adaptation:
– 1) Genetically determined trait
– 2) With survival or reproductive benefit
• How determine trait adaptation? Hard!
Genetic importance
Plants and the Environment
• Genetic basis:
• Heritability (h2): resemblance b/w relatives
(shared genes)
• h 2 = Vg / V p
– Vg = variation due to genotype
– Vp = total phenotypic variation
Plants and the Environment
• 1 approach: slope regression line (r2)
y = mx + b; m is slope
r2=0.52
r2=0
r2=1
Plants and the Environment
• Plant height ex.
(r2)=0.21 or 21%
(h2)=0.21 or 21%
Fig. 6.3
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 __________________
Genetic Variation
• Problem: genetic drift!
Start: 50% mix 2 alleles
Small population (9 inds.)
Large population (50 inds.)
Genetic Variation
• Ex, Wollemi “pine” (Australia)
Loss of Genetic Variability
• Ex, Wollemi “Pine” (Australia)
• Extinct 2 mya, 2 groups found 1994. 40 plants!
Famous quote……
Discoverer
David
Noble
Loss of Genetic Variability
• Ex, Wollemi “Pine” (Australia)
• No measurable genetic diversity!
Collecting seeds
by helicopter
Genetic Variation
• Sources new genetic variation?
– 1) Mutation: Heritable change
– 2)
Plants and the Environment
• Recall:
• Adaptation:
– 1) Genetically determined trait
– 2) With survival or reproductive benefit
• How show benefit? Hard!
Ex
Adaptation Story
• Homoblasty = same
Adaptation Story
• Homoblasty =
• Different
• = heteroblasty
– Also called “juvenile” foliage
• Ex, many Junipers (Juniperus)
Adaptation Story
• Field trip: New Zealand!
• 20% trees heteroblastic
Adaptation Story
• Young plants (0-3 m tall) “divaricate” (
• Older (> 3 m): normal
Pennantia corymbosa
normal
divaricate
Adaptation Story
– Adaptation climate?
– Adaptation herbivores (moas)?
normal
Plagianthus regius
divaricate
Moas?
New Zealand’s Moas
• Ratites (Order)
• 11 spp.
Giant moa
leg bones
Giant moa replica
New Zealand’s Moas
• Hunted extinct by Maori
Adaptation Story
• How study defense hypothesis?
Adaptation Story
• Divaricate: 30-70%
Adaptation Story
• Non-native mammals not affected (shearing teeth)
– Heteroblastic spp. declining
Plants and the Environment
• Recall:
• Adaptation:
– 1) Genetically determined trait
– 2) With survival or reproductive benefit
• How show benefit? Hard!
Variation due to Environment
• Vp = Vg + Ve
Variation due to Environment
• Phenotypic plasticity: vary form/
Variation due to Environment
• Ex, heterophylly: different leaf
– (“hetero”=other; “phyll”=leaf)
Emergent vs.
Submerged leaves
Fig. 6.5
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?
Species
• Species def’n.
– Species: Populations
– Biological species
– Others: cladistics, etc.
Species as ecological tool
• Issues:
– Sp. indicators environmental conditions?
– Plants adapt at sp. level?
– Revegetation/reforestation: does where we obtain
plants matter?
Species
• Good indicators: Ex, Quercus laevis (turkey oak).
Species
• Bad indicators: widespread & variable
• Differences
• How evaluate?
Vp = Vg + Ve