Speciation

Speciation - "a three step process"

  1. Population isolation (gene flow is interrupted):
    1. Allopatric -
      1. gene flow broken by space (geographic barriers).
      2. Kaibab & Abert's squirrel
    2. Sympatric
      1. Gene flow broken for biological reasons (often genetic reasons).
      2. Can work within geographic context
      3. Polyploidy: about 25% of plants - wheat
  2. Divergence in traits
    1. The various mechanisms of microevolution go to work.
  3. Reproductive isolation
    1. Pre-mating barriers (pre-zygotic barriers)
      1. temporal isolation - different breeding times (eastern and western spotted skunks)
      2. different habitats -
      3. behavoiral isolation -
      4. "mechanical" problems - damsel fly
      5. gametic isolation -
    2. Post-mating barriers (post-zygotic barriers)
      1. offspring not viable
      2. zygote inviability
      3. hybrid sterility