The Origin of Species Chapter 24
The Species Problem
The Tempo of Speciation
Modes of Speciation
“It’s a liger”
Morphological
Are ligers a species?
Ecological
Sympatric
Gradualism
Allopatric
Phylogenetic
Biological
Polyploidy
Hybrid Zones
CD Activity (old)
Reproductive Isolation
Autopolyploidy
Prezygotic
Postzygotic
Habitat
Temporal
Reinforcement
Fusion
Reduced
Hybrid fertility
Allopolyploidy
Stability
Behavioral
Mechanical
Gametic
Reduced Hybrid
viability
Hybrid
breakdown
Punctuated
Equilibrium
Original Population
Sympatric Speciation
Allopatric Speciation
Slide 1
“It’s a liger”
napoleon-dynamite-clip8.mov
“bred for its skills and magic”
http://www.youtube.com/watch?v=CD6vpheUoPE
Slide 1
Autopolyploid Speciation
Note: Autopolyploid contains 2X
the amount of Chromosomes than
original species
Allows the formation of a new species from one parental plant.
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Slide 1
Allopolyploid Speciation
Step 1
Note: Allopolyploid contains the
sum total the chromosomes of the 2
parental species 4 + 6 + 10
Allows the formation of a new species of plant with starting
with 2 different plants of different chromosome number
Step 1
Step 2
Step 3
Slide 1
The Gradualism Model
of Evolution
Many slow
changes over
time form a
new species
The Punctuated Equilibrium
Model of Evolution
New species emerge
quickly (punctuated) but
change little over long
periods (equilibrium)
Slide 1
Habitat
Populations
in different
habitats do
not interact
Temporal
Mating or
flowering
in different
times
Behavioral
No attraction
between
males and
females
Mechanical
Sex organs
structures
prevent
reproduction
Prezygotic Barriers
Gametic
Reduced
Reduced
Hybrid Viability Hybrid Fertility
Gametes fail
to interact
Fertilized
zygotes fail
to develop
Hybrids do
not make
functional
gametes
F2 Hybrid
Breakdown
Hybrids
have
reduced
health
Postzygotic Barriers
Slide 1
A. harrisi
A. leucurus
Grand Canyon
South Rim
North Rim
Slide 1
Possible Outcomes for Hybrids in a Hybrid Zone
Strengthening reproductive
barriers…hybrids cease to
form
Weakening reproductive
barriers…the 2 species fuse
Continued production
of hybrid individuals
Slide 1
Example of Reinforcement in Hybrid Zones
Slide 1