Reproductive Isolation

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Reproductive Isolation
Pre-Zygotic prevent fertilization from ever
occurring 1. Temporal different breeding
seasons (frogs) 2. Habitat different areas
(meadows vs. stream side) 3. Behavioral
different courtship (bowerbirds) 4. Mechanical
different reproductive structures (flowers) 5.
Gametic different sperm-egg binding sites
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Reproductive Isolation
Pre-Zygotic prevent fertilization from ever
occurring 1. Temporal different breeding
seasons (frogs) 2. Habitat different areas
(meadows vs. stream side) 3. Behavioral
different courtship (bowerbirds) 4. Mechanical
different reproductive structures (flowers) 5.
Gametic different sperm-egg binding sites
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Reproductive Isolation
Pre-Zygotic prevent fertilization from ever
occurring 1. Temporal different breeding
seasons (frogs) 2. Habitat different areas
(meadows vs. stream side) 3. Behavioral
different courtship (bowerbirds) 4. Mechanical
different reproductive structures (flowers) 5.
Gametic different sperm-egg binding sites
Post-Zygotic prevent functioning adulthood 1.
Hybrid Inviability arrested development 2.
Hybrid Sterility adult not able to
reproduce 3. Hybrid Breakdown F2 sterility
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Allopatric Speciation
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Sympatric Speciation
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Cladogenesis 1 - many
Anagenesis 1 - 1
Species A
Species A
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Adaptive Radiation lots of open niches leads to
rapid speciation
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Getting the Terms Straight
Cause of Speciation pre- and post-zygotic
reproductive isolation
Mechanism of Speciation allopatry vs. sympatry
Pattern of Speciation anagenesis vs. cladogenesis
Pace of Speciation gradualism vs. punctuated
equilibrium
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Accumulation of small changes??
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Exaptations
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Paedomorphosis Neotony
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Developmental Genes (Hox)
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Terms to get straight Reproductive Isolation
(and types) Methods of preventing reproduction
between organisms. (See prior slide for
types.) Allopatry vs. Sympatry Mechanisms of
speciation. Allopatry involves speciation with a
physical barrier while sympatry is speciation in
the same area. Anagenesis vs. Cladogenesis
Patterns of speciation. Anagenesis begins with
one species and ends with one species while
cladogenesis begins with one species and ends
with more than one species. Gradualism vs.
Punctuated Equilibrium Evolutionary paces.
Gradualism involves small, continual changes
resulting in smooth lineages while punctuated
equilibrium involves long periods of stasis with
rapid speciation. Adaptive Radiation Rapid
speciation in response to recently open niches.
Quick exploitation of new, underutilized
resources. Mechanisms for Major Change
Exaptation, Neotony, Paedomorphosis, Hox genes
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Causes of Evolution
Causes of Speciation

• Net Mutation
• Net Migration
• Non-Random Mating
  (i.e., inbreeding or outbreeding)
• Genetic Drift in Small Population
• Natural Selection (choose one from below)
• Stabilizing
• Disruptive
• Directional

• Pre-Zygotic Reproductive Isolation
• Temporal
• Habitat (Spatial)
• Behavioral
• Mechanical
• Gametic Incompatibility
• Post-Zygotic Reproductive Isolation
• Hybrid Inviability
• Hybrid Sterility
• Hybrid Breakdown

Mechanisms
Patterns
Paces

• Allopatry
• Sympatry

• Anagenesis
• Cladogenesis

• Gradualism
• Punctuated Equilibrium