Speciation

Question 1

Biological species concept

Answer 1

Species are groups of interbreeding natural populations that are reproductively isolated from other such groups

Question 2

What prevents closely related species living in the same area from interbreeding?

Answer 2

• Pre-zygotic reproductive isolation
• Post-zygotic reproductive isolation

Question 3

What are pre-zygotic isolating mechanisms?

Answer 3

Mechanisms that prevent interspecific matings

Question 4

What are examples of pre-zygotic isolating mechanisms?

Answer 4

• Potential mates are prevented from meeting (seasonal and habitat isolation)
• Behavioural incompatibilities prevent mating (ethological isolation)
• Copulation attempted but no transfer of sperm takes place (mechanical isolation)

Question 5

What are post-zygotic isolating mechanisms?

Answer 5

Mechanisms that reduce full success of interspecific crosses

Question 6

What are examples of post-zygotic isolating mechanisms?

Answer 6

• Sperm transfer takes place but egg is not fertilised (gametic incompatibility)
• Egg is fertilised but zygote dies (zygotic mortality)
• Zygote develops into an F1 hybrid of reduced viability (hybrid inviability)
• F1 hybrid is fully viable but partially or completely sterile, or produces deficient F2 (hybrid sterility)

Question 7

What theory proposes a genetic mechanism for reduced hybrid fitness?

Answer 7

(Bateson-)Dobzhansky-Muller Theory

Question 8

What factors may affect the rates of speciation?

Answer 8

• organismal traits such as: behaviour, ecology, generation times
• external (environmental) factors affecting the strength of natural selection