Outcomes of evolution

• Natural Selection• Variation within

species

Quaking Aspen: genet and ramets,10,000 yrs old

Variation and natural Selection

Natural Selection

• Requires variation• Heritability• Environmental

change• Adaptive traits• Differential

reproduction

Heritability: Brassica campestris

• Resemblance among relatives due to shared genes

• If offspring matched parents exactly then the correlation would be 1.0

• No relationship would be 0.0

Heritability

• VP= phenotypic variance

• VG= genetic variance • VE= environmental

variance • VP= VG + VE

• H2= VG/VP

• Total genetic contribution to phenotypic variability

Narrow-sense Heritability• Potential response

to selection• Additive variance=

each allele adds equally to the phenotype

• Dominance variance = A is dominant to a so AA and Aa have the same phenotype

• VG= VA + VD

• h2 = VA/ VE + VA + VD

• High h2 prediction of impact of selection in altering a population.

Adaptation

• Any heritable behavioral, morphological or physiological trait

• that maintains or increases the fitness

• of an organism• under a given set of environmental

conditions.

Plasticity

Relative Fitness

• The contribution an organism makes to future generations and the population gene pool.

Types of selection

Directional Stabilizing

Three Patterns

• Specialists: perform best in different environments

• Phenotypically plastic: match the most fit trait value for each set of environmental conditions

• Generalists: converge on a single phenotype intermediate and can survive in all environments

Variation

• Mutation: ultimate source of genetic variation

• Migration: seed and pollen dispersal

• Increase variation

Variation: Genetic drift

Population size important

Migration works to keep nearby clusters the same: pink next to pink whileDistant populations can easily be different.

Small populations will lose variation due to drift

Variation within species

• Clines• Ecotypes • Acclimation

Clines• Heavy Metal

tolerance• Gradient over short or

long distance• Trade-off grow well in

contaminated soil, poor growth in normal soil

• Reduce cross pollination

Mine tailing individuals flower earlierPlants near boundary self pollinate

Ecotypes

• Ecotypes: populations of a species from different habitats/locations that possess genetically based differences in appearance or function

Height variation

Achillea lanulosa

• three gardens • 4 ecotypes • Results in common

gardens • Mather population

(1400 m) grown in different gardens

• Inherited variation

Timberline, Mather & Stanford

Differences• Morphology (growth

form, leaves)• Phenology (timing of

flowering, dormancy)• Mather: thinner

boundary layer, close to air temperature

• Timberline: compact, thicker boundary layer, warmer

Ecophysiological variation

• Sorrel (Oxyria digyna)• Alpine and arctic • Enzyme data • Acclimation

Photosynthetic response

Enzyme data

• Enzyme response to incubation at 50oC• Environmental preconditions

Summary

• Heritable variation• Selection• Trade-offs• Co-evolution species interactions