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Genetic Variation and Adaptation in Plants: Evolutionary Insights

Explore the genetic basis of plant traits and how plants adapt to their environment through genetic variation. Learn about adaptation stories and the impact of genetic drift on plant populations.

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Genetic Variation and Adaptation in Plants: Evolutionary Insights

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  1. Ch. 6: Evolutionary Processes/Outcomes

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

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

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

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

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

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

  8. 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

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

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

  11. 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 __________________

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

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

  14. Loss of Genetic Variability • Ex, Wollemi “Pine” (Australia) • Extinct 2 mya, 2 groups found 1994. 40 plants! Discoverer David Noble Famous quote……

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

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

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

  18. Adaptation Story • Homoblasty = same

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

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

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

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

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

  24. New Zealand’s Moas • Hunted extinct by Maori

  25. Adaptation Story • How study defense hypothesis?

  26. Adaptation Story • Divaricate: 30-70%

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

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

  29. Variation due to Environment • Vp = Vg + Ve

  30. Variation due to Environment • Phenotypic plasticity: vary form/

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

  32. 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?

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

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

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

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

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