The Origin of Species

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• This planetary nebula, NGC 6751, was formed
  several thousand years ago when the star in its
  center ejected some of its material.
• Planetary nebulae look like planets in small
  telescopes (plus are found hanging around stars).
  
• They are clouds of gas thrown off by stars that
  are nearing the ends of their lives.
• There is no need for concern however our own Sun
  will only eject a planetary nebula like this
  around 6 billion years from now.
• The blue areas in this picture are the hottest
  glowing gas. The orange and red areas are cooler.
  
• NGC 6751 is 0.8 light-years in diameter, 600
  times the diameter of our own solar system.

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Species Concepts

• Biological Species Concept
• Reproductive Isolation
• Not necessarily easy to apply
• Morphological Species Concept
• Phenotypic differences (fossil species)
• Recognition Species Concept
• Mating recognition
• Cohesion Species Concept
• Persistence of discrete phenotypes
• Ecological Species Concept
• Filling of ecological niches
• Competition for resources
• Evolution Species Concept
• Evolutionary lineages
• Pluralistic Species Concept
• Combinations of above as appropriate

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Patterns of Speciation
Branching Evolution
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Patterns of Speciation
Branching Evolution
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Patterns of Speciation
Branching Evolution
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Reproductive Isolation

• Geographical Isolation
• Habitat Isolation
• Behavioral Isolation
• Temporal Isolation
• Mechanical Isolation
• Gametic Isolation
• Reduced Hybrid Viability
• Reduced Hybrid Fertility
• Hybrid Breakdown

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Reproductive Isolation
speciation results from experiencing or
avoding the cost of bearing reduced-fitness hybrid
progeny
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Postzygotic Isolation

• Geographical Isolation
• Habitat Isolation
• Behavioral Isolation
• Temporal Isolation
• Mechanical Isolation
• Gametic Isolation
• Reduced Hybrid Viability
• Reduced Hybrid Fertility
• Hybrid Breakdown

Follows Conception (conception is costly)
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Prezygotic Isolation

• Geographical Isolation
• Habitat Isolation
• Behavioral Isolation
• Temporal Isolation
• Mechanical Isolation
• Gametic Isolation
• Reduced Hybrid Viability
• Reduced Hybrid Fertility
• Hybrid Breakdown

Prevents Conception (conception is costly)
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Genetic Contribution

• Geographical Isolation
• Habitat Isolation
• Behavioral Isolation
• Temporal Isolation
• Mechanical Isolation
• Gametic Isolation
• Reduced Hybrid Viability
• Reduced Hybrid Fertility
• Hybrid Breakdown

Genetic Contribution implies is Product of
Evolution
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Hybridization Attempted
Mating is Costly (even if no conception)

• Geographical Isolation
• Habitat Isolation
• Behavioral Isolation
• Temporal Isolation
• Mechanical Isolation
• Gametic Isolation
• Reduced Hybrid Viability
• Reduced Hybrid Fertility
• Hybrid Breakdown

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Increasing Fitness Costs

• Geographical Isolation
• Habitat Isolation
• Behavioral Isolation
• Temporal Isolation
• Mechanical Isolation
• Gametic Isolation
• Reduced Hybrid Viability
• Reduced Hybrid Fertility
• Hybrid Breakdown

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Allopatric Speciation
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Geographical Barrier
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Peripheral Isolates
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Peripheral Isolation

• Peripheral populations
• may be different from the parental population
  before becoming separated (? different
  environments/extremes of range/clines ? natural
  selection for phenotypic divergence)
• may be founded by only a small number of
  individuals (? founder effects ? genetic drift
  leading to divergence of populations)
• may not have an opportunity to increase in size
  over the medium term (? bottleneck effect ?
  genetic drift leading to divergence of
  populations)
• may find themselves in environments that differ
  from that of the parental population (? natural
  selection for phenotypic divergence)

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Scenario for Allopatric Speciation
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Allopatric Speciation on Islands
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Ring species
Subspecies may be populations caught in the act
of speciating

• Subspecies are morphologically distinct from
  other subspecies of the same species
• Members of subspecies are more likely to breed
  with their own subspecies than with other members
  of their species
• Subspecies are geographically localized

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Sympatric Speciation
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Sympatric Speciation
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Isolation due to Autopolyploidy
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Isolation due to Allopolyploidy
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Hybrid Zone
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Introgression
Introgression low level gene flow between
otherwise reproductively isolated populations
But even though F1 shows reduced fitness that
does not mean a fitness of zero ? thus mating and
gene exchange back to parental populations can
still occur
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Introgression
On the other hand, if the backcross has
sufficiently low fitness then introgression will
not occur
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Punctuated Equilibrium
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Species Selection

• Various Microevolutionary processes have
  Macro-evolutionary counterparts
• Birth of individual (microevolution) ? Birth of
  species, i.e., Speciation (macroevolution)
• Death of individual (microevolution) ? Extinction
  of species (macroevolution)
• Genetic drift (microevolution) ? Species
  extinction due to random (not foreseeable) events
  (macroevolution)
• Natural selection (microevolution) ? Differential
  rates of speciation and extinction due to factors
  intrinsic to lineages, i.e., Species selection
  (macroevolution)
• These processes are analogous rather than
  identical (in the sense that the
  microevolutionary process does not necessarily
  give rise to the macroevolutionary process)

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Species Selection

• Things that make a species more fit over the
  short term (e.g., specialization) do not
  necessarily give rise to greater rates of
  speciation or lower rates of extinction within
  lineages
• In other words, there is a reason that
  generalists persist despite the fact that
  specialists typically are more fit to the
  environments in which they evolved
• Other characteristics of a species might also
  make that species less susceptible to random
  changes in the environment (e.g., asteroid
  impact) such characteristics might include small
  size and wide range as well as a lack of specific
  dietary needs, etc.
• "The species that endure the longest and generate
  the greatest number of new species determine the
  direction of major evolutionary trends."
• Thus, to impact greatly on the evolution of the
  diversity of life, an organism must possess
  qualities that go beyond simply being highly
  adapted to life within a specific environment

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Link to Next Presentation
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Acknowledgements
http//207.233.
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Subspecies

• Subspecies are morphologically distinct from
  other subspecies of the same species
• Members of subspecies are more likely to breed
  with their own subspecies than with other members
  of their species
• Subspecies are geographically localized

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Subspecies
Mountain Zebra (u.l.) Grevy Zebra (u.r.) Plains
Zebra (l.l.) Quagga (l.r., extinct)
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Subspecies

• Florida Panther
• Mountain Lion

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Subspecies (bye bye) ?

• Some researchers argue that the subspecies
  concept is sufficiently flawed as to be
  irrelevant
• It doesnt really matter because apparently the
  rallying cry of humanity goes something like
  this Prosperity before subspecies
• If you really want a good cry, try doing a
  subspecies and extinct search on the web you
  will find things like, Three tiger subspecies
  are now extinct all of them are completely
  dead Caspian tiger (P.I. virgata), Javan tiger
  (P.t. sondaica), Bali tiger (P.t. balica).

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Subspecies
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Scenario for Allopatric Speciation
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Allometric Growth
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Paedomorphosis
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Geological Time
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Taxonomic Categories