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Speciation in animals Allopatric speciation: vicariance – Biogeography Colonisation of Surtsey 1963-2003 Sympatric speciation – Rhagoletis pomonella Parapatric.

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Presentation on theme: "Speciation in animals Allopatric speciation: vicariance – Biogeography Colonisation of Surtsey 1963-2003 Sympatric speciation – Rhagoletis pomonella Parapatric."— Presentation transcript:

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 Crucial event: Reproductive isolation (barrier to gene flow) Prezygotic isolation Habitat, seasonal, sexual, mechanical, gamete viability Postzygotic isolation Inviability or sterility of hybrids

3 Sympatric speciation Speciation in the absence of spatial isolation Polymorphism established selection favouring prezygotic isolation Genetic causes: pleiotropy & hitch-hiking

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

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


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