1. Speciation in animals Allopatric speciation: vicariance
Biogeography
Colonisation of Surtsey
Sympatric speciation
Rhagoletis pomonella
Parapatric speciation
Carrion crow & hooded crow

2. Speciation in animals
Crucial event: Reproductive isolation (barrier to gene flow)
Prezygotic isolation
Habitat, seasonal, sexual, mechanical, gamete viability
Postzygotic isolation
Inviability or sterility of hybrids
Pleiotropy: Lets say that there is a gene controlling bird beak size. Selection on bird beak size due to efficiency of feeding (different food preferences) and also due to sexual choice. Therefore, an allele favoured due to an ecological adaptation (food preference) will also cause reproductive isolation due to sexual choice.
Hitch-hiking: a gene at one locus is selected by natural selection, an allele at a linked locus simply rides along.

3. Sympatric speciation Speciation in the absence of spatial isolation
Polymorphism established  selection favouring prezygotic isolation
Genetic causes: pleiotropy & hitch-hiking
Pleiotropy: Lets say that there is a gene controlling bird beak size. Selection on bird beak size due to efficiency of feeding (different food preferences) and also due to sexual choice. Therefore, an allele favoured due to an ecological adaptation (food preference) will also cause reproductive isolation due to sexual choice.
Hitch-hiking: a gene at one locus is selected by natural selection, an allele at a linked locus simply rides along.

4. Rhagoletis pomonella: sympatric speciation via host shift
N. American R. pomonella lays eggs in hawthorn fruit
In 1864: R. pomonella first found on apples in New York State
Hawthorn  Apple host shift

5. Rhagoletis pomonella: sympatric speciation via host shift
Today: hawthorn vs. apple associated R. pomonella populations genetically distinct

6. Parapatric speciation
Adjacent but non-overlapping distributions
Allopatric minus the geographical barrier
Clines
Reproductive barriers? – sub species, hybrids
Hybrid zone
Rapid speciation in the face of environmental change?

7. The hybrid zone of the hooded and carrion crows (Corvus corone & C
The hybrid zone of the hooded and carrion crows (Corvus corone & C. corax) in Europe
Interbreeding occurs in hybrid zone  speciation incomplete?
A hybrid zone is also a tension zone if the hybrids are selectively disadvantageous