1. Plant Ecology - Chapter 6
Outcomes of Natural Selection

2. Phenotypic Variation
Natural selection acts on phenotypic variation, selecting against traits that are poorly adapted to the existing environment

3. Phenotypic Variation
For natural selection to act, phenotypic variation must be heritable (have a genetic basis), and must produce fitness differences

4. Phenotypic Variation Directional selection Stabilizing selection
Disruptive selection

5. Genotype-Environment Interactions
Differences among individuals with different genotypes may depend on the environment
Different expressions

6. 3 Patterns of Adaptation
1) Different phenotypes specialize in different environments
2) Phenotypic plasticity to match environments
3) Single phenotype for all environments - passable

7. Level of Selection
Natural selection occurs at the level of the individual
Genet or ramet?
Individual ramets may come and go, but genets can exist for long time
Quaking aspen years vs. 10,000 years

8. Increasing Variation
Mutations - 10% of individuals in most plant populations have new mutations each generation
Migration - spores, pollen, seeds can add new variation to populations

9. Decreasing Variation Natural selection -reduce genetic variation
Genetic drift - change in gene frequencies do to random sampling effects - small populations most affected

10. Variation Among Populations
Mutation and genetic drift increase variation among populations
Natural selection can increase or decrease variation among populations
Migration decreases variation among populations

11. Ecotypes
Populations of a species from different habitats, that possess genetically based differences in appearance, function
Differences in characteristics retained when all grown together in same environment

12. Speciation Allopatric, parapatric, sympatric
Common to both plants and animals

13. Speciation
Hybridization - rare, but very frequent in some genera - e.g., oaks
New genetic combinations possibly adapted to different environmental conditions than either parent species
Polyploidy - duplication of entire set of chromosomes - instant reproductive isolation