Species and Speciation

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Species and Speciation
D. melanogaster
D. simulans
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Species and Speciation I. Species Concepts
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Species and Speciation I. Species Concepts How
we define a species depends on the goal we have
in mind.
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Species and Speciation I. Species Concepts How
we define a species depends on the goal we have
in mind. Are we categorizing existing or fossil
organisms?
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Species and Speciation I. Species Concepts How
we define a species depends on the goal we have
in mind. Are we categorizing existing or fossil
organisms? Are we trying to understand
correlates between populations adapting to
different environments?
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Species and Speciation I. Species Concepts How
we define a species depends on the goal we have
in mind. Are we categorizing existing or fossil
organisms? Are we trying to understand
correlates between populations adapting to
different environments? Are we trying to
reconstruct phylogenies?
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Species and Speciation I. Species Concepts A.
Morphological Species Concept
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Species and Speciation I. Species Concepts A.
Morphological Species Concept -
Categorical/'essential' in a platonic sense
based on morphological similarity to a 'type'
specimen
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Species and Speciation I. Species Concepts A.
Morphological Species Concept -
Categorical/'essential' in a platonic sense
based on morphological similarity to a 'type'
specimen - Useful, but many species are
polymorphic and some sibling species are
indistinguishable morphologically.
H. erato
D. melanogaster (M)
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Species and Speciation I. Species Concepts A.
Morphological Species Concept -
Categorical/'essential' in a platonic sense
based on morphological similarity to a 'type'
specimen - Useful, but many species are
polymorphic and some sibling species are
indistinguishable morphologically. -
Nonetheless, for dead or fossilized specimens,
the phenotype is all we might have to analyze. As
such, there are ways of quantifying the phenotype
and defining "phenetic" species... by quantifying
the within-group phenotypic variation,
statistical analysis can ascertain whether a
novel individual lies within that typical range.
New Species!!
old species
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Species and Speciation I. Species Concepts A.
Morphological Species Concept -
Categorical/'essential' in a platonic sense
based on morphological similarity to a 'type'
specimen - Useful, but many species are
polymorphic and some sibling species are
indistinguishable morphologically. -
Nonetheless, for dead or fossilized specimens,
the phenotype is all we might have to analyze. As
such, there are ways of quantifying the phenotype
and defining "phenetic" species... by quantifying
the within-group phenotypic variation,
statistical analysis can ascertain whether a
novel individual lies within that typical range.
Problem... need a pretty good sample to describe
within-group variation with confidence.
old species
New Species?
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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942

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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potentially interbreeding
  populations that are reproductively isolated from
  other such groups"

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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potetially interbreeding
  populations that are reproductively isolated from
  other such groups"
• - Biological units are genetically defined
  reproductive isolation makes populations
  different from one another, creating new units.
  So, reproductive isolation is the key
  characteristic of a species.

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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potetially interbreeding
  populations that are reproductively isolated from
  other such groups"
• - Biological units are genetically defined
  reproductive isolation makes populations
  different from one another, creating new units.
  So, reproductive isolation is the key
  characteristic of a species.
• - Limitations

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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potetially interbreeding
  populations that are reproductively isolated from
  other such groups"
• - Biological units are genetically defined
  reproductive isolation makes populations
  different from one another, creating new units.
  So, reproductive isolation is the key
  characteristic of a species.
• - Limitations
• - Process may be continuous - where do you
  draw the "line" of isolation?

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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potetially interbreeding
  populations that are reproductively isolated from
  other such groups"
• - Biological units are genetically defined
  reproductive isolation makes populations
  different from one another, creating new units.
  So, reproductive isolation is the key
  characteristic of a species.
• - Limitations
• - not applicable to asexual species

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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potetially interbreeding
  populations that are reproductively isolated from
  other such groups"
• - Biological units are genetically defined
  reproductive isolation makes populations
  different from one another, creating new units.
  So, reproductive isolation is the key
  characteristic of a species.
• - Limitations
• - not applicable to asexual species
• - hybridization occurs in nature, even between
  otherwise 'good' species. Natural variability is
  not strictly discontinuous, so pigeon-holing on
  any grounds will be wrong in some cases. It
  becomes a matter of degree. The best example are
  "Ring Complexes"...series of species which breed
  with neighboring species but the 'end' species do
  not. Salamanders in California, Gulls in
  circumpolar regions.

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• Ring Species

Divergence that correlates with geographical
distance can create interesting patterns on a
spherical globe, or around a geographical feature.
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• Ring Species

Divergence that correlates with geographical
distance can create interesting patterns on a
spherical globe, or around a geographical feature.
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• Ring Species

Divergence that correlates with geographical
distance can create interesting patterns on a
spherical globe, or around a geographical feature.
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• Species and Speciation
• I. Species Concepts
• A. Morphological Species Concept
• B. Biological Species Concept - Mayr 1942
• "Groups of actually or potetially interbreeding
  populations that are reproductively isolated from
  other such groups"
• - Biological units are genetically defined
  reproductive isolation makes populations
  different from one another, creating new units.
  So, reproductive isolation is the key
  characteristic of a species.
• - Limitations
• - not applicable to asexual species
• - hybridization occurs in nature, even between
  otherwise 'good' species. Natural variability is
  not strictly discontinuous, so pigeon-holing on
  any grounds will be wrong in some cases. It
  becomes a matter of degree. The best example are
  "Ring Complexes"...series of species which breed
  with neighboring species but the 'end' species do
  not. Salamanders in California, Gulls in
  circumpolar regions.
• - Allopatric populations Potential
  interbreeding means that populations that are
  spatially separated and morphologically/geneticall
  y distinct may be in the same species.

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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat)
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation

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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates
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Species and Speciation I. Species Concepts II.
Recognizing Species III. Making Species -
Reproductive Isolation A. Pre-Zygotic
Barriers 1. Geographic Isolation (large scale or
habitat) 2. Temporal Isolation 3. Behavior
Isolation - don't recognize one another as mates
4. Mechanical isolation - genitalia don't fit

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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates 4. Mechanical isolation -
genitalia don't fit 5. Gametic Isolation -
gametes transfered but sperm can't fertilize egg

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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates 4. Mechanical isolation -
genitalia don't fit 5. Gametic Isolation -
gametes transfered but sperm can't fertilize egg
B. Post-Zygotic Isolation
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates 4. Mechanical isolation -
genitalia don't fit 5. Gametic Isolation -
gametes transfered but sperm can't fertilize egg
B. Post-Zygotic Isolation 1. Genomic
Incompatibility - zygote dies
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates 4. Mechanical isolation -
genitalia don't fit 5. Gametic Isolation -
gametes transfered but sperm can't fertilize egg
B. Post-Zygotic Isolation 1. Genomic
Incompatibility - zygote dies 2. Hybrid
Inviability - F1 has lower survival
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates 4. Mechanical isolation -
genitalia don't fit 5. Gametic Isolation -
gametes transfered but sperm can't fertilize egg
B. Post-Zygotic Isolation 1. Genomic
Incompatibility - zygote dies 2. Hybrid
Inviability - F1 has lower survival 3. Hybrid
Sterility - F1 has reduced reproductive success

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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation A.
Pre-Zygotic Barriers 1. Geographic Isolation
(large scale or habitat) 2. Temporal Isolation
3. Behavior Isolation - don't recognize one
another as mates 4. Mechanical isolation -
genitalia don't fit 5. Gametic Isolation -
gametes transfered but sperm can't fertilize egg
B. Post-Zygotic Isolation 1. Genomic
Incompatibility - zygote dies 2. Hybrid
Inviability - F1 has lower survival 3. Hybrid
Sterility - F1 has reduced reproductive success
4. F2 breakdown - F1's survive but F2's have
incompatible combo's of genes
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation III.
Speciation
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation III.
Speciation Speciation is not a goal, or a
selective product of adaptation. It is simply a
consequence of genetic changes that occurred for
other reasons (selection, drift, mutation, etc.).
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation III.
Speciation A. Modes
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Species and Speciation I. Species Concepts II.
Making Species - Reproductive Isolation III.
Speciation A. Modes 1. Allopatric
Divergence in geographically separate
populations - Vicariance - range divided by new
geographic feature
A
B
C
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III. Speciation A. Modes 1. Allopatric
Divergence in geographically separate
populations - Vicariance - range divided by new
geographic feature - Peripatric - divergence of
a small migrant population
A
B
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III. Speciation A. Modes 1. Allopatric
Divergence in geographically separate
populations - Vicariance - range divided by new
geographic feature - Peripatric - divergence of
a small migrant population 2. Parapatric -
neighboring populations diverge, even with gene
flow
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III. Speciation A. Modes 1. Allopatric
Divergence in geographically separate
populations - Vicariance - range divided by new
geographic feature - Peripatric - divergence of
a small migrant population 2. Parapatric -
neighboring populations diverge, even with gene
flow
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2. Parapatric - neighboring populations diverge,
even with gene flow
Hybrid Backcross??
Hybrid
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III. Speciation A. Modes 1. Allopatric
Divergence in geographically separate
populations - Vicariance - range divided by new
geographic feature - Peripatric - divergence of
a small migrant population 2. Parapatric -
neighboring populations diverge, even with gene
flow 3. Sympatric Divergence within a single
population
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3. Sympatric Divergence within a single
population Maynard Smith (1966) - hypothesized
this was possible if there was disruptive
selection within a population - perhaps as a
specialist herbivore/parasite colonized and
adapted to a new host.
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3. Sympatric Divergence within a single
population Maynard Smith (1966) - hypothesized
this was possible if there was disruptive
selection within a population - perhaps as a
specialist herbivore/parasite colonized and
adapted to a new host. Example Hawthorn/Apple
Maggot Fly (Rhagoletis pomonella)
Hawthorn maggot fly is a native species that
breeds on Hawthorn (Crataegus sp.)
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3. Sympatric Divergence within a single
population Maynard Smith (1966) - hypothesized
this was possible if there was disruptive
selection within a population - perhaps as a
specialist herbivore/parasite colonized and
adapted to a new host. Example Hawthorn/Apple
Maggot Fly (Rhagoletis pomonella)
Europeans brought apples to North America. They
are in the same plant family (Rosaceae) as
Hawthorn.
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3. Sympatric Divergence within a single
population Maynard Smith (1966) - hypothesized
this was possible if there was disruptive
selection within a population - perhaps as a
specialist herbivore/parasite colonized and
adapted to a new host. Example Hawthorn/Apple
Maggot Fly (Rhagoletis pomonella)
Europeans brought apples to North America. They
are in the same plant family (Rosaceae) as
Hawthorn. In 1864, apple growers noticed
infestation by Apple Maggot flies...which were
actually just "hawthorn flies"...
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3. Sympatric Divergence within a single
population Maynard Smith (1966) - hypothesized
this was possible if there was disruptive
selection within a population - perhaps as a
specialist herbivore/parasite colonized and
adapted to a new host. Example Hawthorn/Apple
Maggot Fly (Rhagoletis pomonella)
races breed on their own host plant, and have
adapted to the different seasons of fruit
ripening. Only a 4-6 hybridization
rate. Temporal, not geographic, isolation.
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III. Speciation A. Modes B. Speciation
Rate Some characteristics should increase the
chances that a species radiates.... - high
dispersal capacity (increase geographic
isolation) - small (more likely to become
isolated) - produce lots of offspring (more
successful colonists)
INSECTS in general, and Beetles in particular....
they fly (disperse), but poorly (don't
return...isolation). And they are tough as nails,
so they can survive to wherever they disperse.
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III. Speciation A. Modes B. Speciation
Rate
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III. Speciation A. Modes B. Speciation
Rate Some characteristics should increase the
chances that a species radiates....
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III. Speciation A. Modes B. Speciation
Rate Some characteristics should increase the
chances that a species radiates.... - high
dispersal capacity (increase geographic
isolation)
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III. Speciation A. Modes B. Speciation
Rate Some characteristics should increase the
chances that a species radiates.... - high
dispersal capacity (increase geographic
isolation) - small (more likely to become
isolated)
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III. Speciation A. Modes B. Speciation
Rate Some characteristics should increase the
chances that a species radiates.... - high
dispersal capacity (increase geographic
isolation) - small (more likely to become
isolated) - produce lots of offspring (more
successful colonists)
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III. Speciation A. Modes B. Speciation
Rate Some characteristics should increase the
chances that a species radiates.... - high
dispersal capacity (increase geographic
isolation) - small (more likely to become
isolated) - produce lots of offspring (more
successful colonists)
INSECTS in general, and Beetles in particular....
they fly (disperse), but poorly (don't
return...isolation). And they are tough as nails,
so they can survive to wherever they disperse.
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III. Speciation A. Modes B. Speciation
Rate - so speciation can be instantaneous -
speciation can occur as a function of selective
pressure and pop size (drift and selection in
peripatric speciation) - and the rate can be
influenced by the characteristics of the species,
themselves. So, although genetic change may
be constant within genes, the efftc that these
changes have on reproductive isolation can vary
dramatically... speciation is not a
uniformitarian process...