Speciation

Ch 14

What is a species

• Numerous definitions• Biological Species Concept• Morphological Species Concept• Ecological Species Concept• Phylogenic Species Concept

Evolutionary Theories

Creating a Species

• Reproductive Isolation• Reproductive Barriers– Prezygotic Barriers– Postzygotic Barriers

Prezygotic Barriers

• Temporal Isolation• Habitat Isolation• Behavioral Isolation• Mechanical Isolation• Gametic Isolation

Postzygotic Barriers

• Reduced Hybrid Viability• Reduced Hybrid Fertality• Hybrid Breakdown

Speciation

• Emergence of a new species• Allopatric vs Sympatric– Creation of reproductive barriers

Parent species2n = 6

Tetraploidcells

4n = 12

1

Diploidgametes

2n = 6

2

Viable, fertiletetraploidspecies4n = 12

Self-fertilization

3

Sympatric Speciation• Niche separation, sexual selection, habitat

differentiation• Polyploid

Sympatric Speciation• Hybrid Polypoid

Species A2n = 4

Gameten = 2

1 2

Species B2n = 6

Gameten = 3

Sterile hybridn = 5

Chromosomes nothomologous(cannot pair)

Viable, fertilehybrid species

2n = 10

3

Hybrid Zones

• Regions where different species meet and mate

• Outcomes– Reinforcement– Fusion– Stability

Adaptive Radiation

• Evolution of diverse species from common ancestor

• Colonization• Extinctions

• http://www.youtube.com/watch?v=YCoEiLOV8jc

• http://www.youtube.com/watch?v=v9i2WYS60L4