Natural Selection

Genetic Variation

• created by mutation

• rearranged by

  • migration

  • recombination

• reduced/differentiared by:

  • drift (stochastic (random) process)

  • Selection

Adaptive evolutionary change = selection

• selection: differential survival or reproduction of different genotypes

• only selection leads to adaptive genetic change: by increasing the frequency of beneficial alleles

• adaptive evolution means the population is, on average, better able to cope with the conditions it faces

Examples of traits that have been documented to show adaptive evolution in animals:

• Morphology, behavior, color, disease resistance, body size

Rapid adaptive evolution

• rabbits - exotic pest in Australia

• myxoma virus introduced to control rabbits in 1950

• Results

  • rabbits evolve resistance (after 99% mortality)

  • virus evolves to be less virulent (better transmission)

• if diff genotypes had equal probability of surviving and passing on their alleles then we wouldn’t be worried about genetic variation in conservation

• but genetic changes associated with bottlenecks often increase the frequency of alleles that reduce an individuals probability of surviving to reproduce

• and some alleles and genotypes affect survivorship/reproductive success differently, depending on env.

  • genetic diffs among local pops may be important for local persistence

• most models rely on the assumption of neutrality

• ex. loss of H = 1/2N

• how to account for selection

• depends on the locus, the pattern and intensity of natural selection

• dont have these values, so cant