Reproductive Isolation: Interruption of Gene Flow

1
Reproductive IsolationInterruption of Gene Flow

• Isolating mechanisms
• Pre-mating / Pre-zygotic? prevent formation of
  hybrid zygotes
• Post-mating / Post-zygotic? reduce viability or
  fertility of hybrid zygotes

2
Isolating Mechanisms1. Pre-zygotic
a. Ethological / Sexual Isolation
Green lacewings
3
Isolating Mechanisms1. Pre-zygotic
b. Different Pollinator Isolation
4
Isolating Mechanisms1. Pre-zygotic
c. Seasonal/Temporal Isolation
5
Isolating Mechanisms1. Pre-zygotic
d. Mechanical Isolation
Platanthera chlorantha eye placement
Platanthera bifolia proboscis placement
6
Isolating Mechanisms1. Pre-zygotic
e. Ecological/Habitat Isolation
Xenopus gilli
Xenopus laevis
7
Isolating Mechanisms2. Post-zygotic
a. Hybrid Inviability
Rana sylvatica
Rana pipiens
? hybrids dont survive for more than a day
8
Isolating Mechanisms2. Post-zygotic
b. Hybrid Sterility


Donkey
Mule
Horse
? Mules usually dont develop fertile sperm
9
Isolating Mechanisms2. Post-zygotic
c. Hybrid Breakdown
Nasonia vitripennis
Nasonia giraulti
? the F2 or backcross hybrids have reduced
viability/fertility
10
Lion TigerPre-zygotic or Post-zygotic?
Panthera leo
Panthera tigris
11
Lion TigerPre Post-zygotic
liger
tigon
12
Human ApePre-zygotic Post-zygotic

• Surprisingly little evidence ranges from
  conspiracy to myth (ethical issues prevent
  clarity)

13
Human ApePre-zygotic Post-zygotic

• Surprisingly little evidence ranges from
  conspiracy to myth (ethical issues prevent
  clarity)
• Unlikely because of chromosome differences