What is speciation?

Speciation is the process by which new species arise from pre-existing ones over time. When two populations are no longer capable of mating to produce fertile offspring, they are considered to be separate species.

Speciation can be allopatric (when a population is geographically split) or sympatric (occurring while being in the same geographical area)

How allopatric speciation occurs

  1. Two populations are separated by a geographical barrier. (geographical isolation)
  2. Different mutations occur on both populations.
  3. Different selection pressures act on both populations.
  4. Frequencies of different alleles increase in the gene pools of both populations.
  5. Both populations do not interbreed (reproductive isolation) and there is no gene flow. 
  6. Over many generations, the populations develop into different species.

How sympatric ecological speciation occurs

  1. A population splits into two subpopulations that live in different microhabitats.
  2. They experience different microclimates and have different food sources.
  3. Different selection pressures act on both subpopulations.
  4. Frequencies of different alleles increase in the gene pools of both subpopulations.
  5. Individuals of one subpopulation rarely move out of their microhabitat. 
  6. Both populations do not interbreed (reproductive isolation) and there is no gene flow.
  7. Over many generations, the populations develop into different species.

How sympatric behavioural speciation occurs

  1. A population splits into two subpopulations that live in different areas in the same habitat.
  2. The two subpopulations experience different mutations.
  3. Different selection pressures act on both subpopulations.
  4. Frequencies of different alleles increase in the gene pools of both subpopulations.
  5. Morphological changes to features used in attracting mates/changes in mating rituals occur.
  6. Both subpopulations no longer respond to each other’s mating rituals. (pre-zygotic isolation)
  7. Both subpopulations do not interbreed (reproductive isolation) and there is no gene flow. 
  8. Over many generations, the populations develop into different species.
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