Transcript Document

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
• Vg = variation due
• Ve = variation due
Focus Vg
Plants and the Environment
• Adaptation:
– 1) Genetically
– 2) With
• How determine trait adaptation? Hard!
Genetic importance
Plants and the Environment
• Genetic basis:
• Heritability (h2): resemblance between relatives
due
• h 2 = V g / Vp
– Vg = variation due to
– Vp = total
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 (change genetic makeup)
– 2) Dominant alleles mask “lethal recessives:” fatal if
Finish this sentence:
If you were haploid you’d be __________________
Genetic Variation
• Problem: genetic drift! Loss
• Small pop’ns
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.
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
. Rare: 10% of
pop’n. each generation (new mutation)
– 2) Immigration.
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 twig/leaf forms
Adaptation Story
• Homoblasty = same
• Different twig/leaf forms (plant age) = heteroblasty
– Also called “juvenile”
• Ex, many Junipers (Juniperus)
Adaptation Story
• Young plants (0-3 m tall) “divaricate” (wide-angled)
•
• 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 species
Giant moa
leg bones
Giant moa replica
New Zealand’s Moas
• Hunted extinct by Maori
Adaptation Story
• How study defense hypothesis?
• Other
Adaptation Story
• Divaricate: 30-70% less loss
• Branches resist
• Divaricate
Adaptation Story
• Non-native mammals not affected (shearing teeth)
– Heteroblastic species 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/physiology
Variation due to Environment
• Ex, heterophylly: different
– (“hetero”=other; “phyll”=leaf)
Emergent vs.
Submerged leaves
Fig. 6.5
Species as ecological tool
• Now: species as tool
• Issues:
– Species indicators
– Plants adapt at
– Revegetation/reforestation: does where
Species
• Species def’n.
– Species: Populations morphologically
similar &
– Biological species approach
– Others: cladistics, etc.
Species
• Good indicators: Ex, Quercus laevis (turkey oak). Dry
sandy soils (sandhills)
Species
• Bad indicators: widespread
• Differences genetic (
environmental (
• How evaluate?
?) or
?)
Vp = Vg + Ve