0: The Species Scape

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0 The Species Scape
A major challenge is to understand how all these
species originated
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2Two types of evolutionary change
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Making babies is hard work!
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4 Examples of isolation
geographic
temporal
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5 Geography of speciation
Sympatry ( same land) speciation occurs in the
same area
Allopatry ( other land) species divergence
happens in geographically isolated areas
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6 Allopatric speciation
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6a Allopatric speciation
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7 Geographic isolation
Two species of antelope squirrels isolated by the
Grand Canyon
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8. Geographic differentiation
Differentiation in the butterfly, Erebia epiphron
in the European mountains. Different colors
designate different races or forms
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11. Founder event speciation
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Allopatric speciation the same event can affect
many lineages at once
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12 Allopatric speciation may affect many
lineages at the same time
Seven snapping shrimp lineages have split into
species pairs after the Isthmus closed.
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13 Host-parasite cospeciation
A
B
C
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14 Sympatric speciation
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15 Normal sexual reproduction(meiosis reduces
the number of sets of chromosomes)
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16 Autopolyploidy (meiosis fails)
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17 Why is it a new species?
Cant breed with its parent due to mismatch in
chromosome number
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19 Allopolyploidy has been important in wheat
evolution
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20 Hybridisation in animals
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Diversifying selection
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22 Types of selection
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23Disruptive (diversifying) selection and
speciation
This could cause speciation if there is a link
between the trait undergoing disruptive selection
and assortative mating
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24 Apple maggot fly (Rhagoletis)

• Native host is Hawthorne tree.
• Larvae develop on fruit.
• Adults mate, deposit eggs on host plant.
• 1860s discovered on apples.
• Different fruiting time
• Temporal Isolation
• 1960s discovered on cherries.
• Different fruiting time
• Temporal isolation

Overall, matings between hawthorn and apple flies
has been reduced to only 6 and the two are now
considered incipient species (sympatric
speciation)
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Is it really sympatric speciation?
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25 Cichlid fish in African lakes sympatric or
allopatric speciation?

• Lake Victoria was dry some 12,400 years ago, yet
  500 cichlid fish species evolved since then.
• Allopatric speciation altering lake levels
  results in smaller lakes forming, isolating
  populations.
• Sympatric speciation sexual selection drives
  speciation
• Postscript Human pollution is breaking down
  reproductive isolation by increasing the
  cloudiness of the lake's waters

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27 Summary

• Two kinds of evolutionary change anagenesis and
  cladogenesis
• Speciation can occur in allopatry or sympatry
• Allopatric speciation isolates populations
  geographically
• Sympatric speciation isolates populations in
  time, microhabitat or behaviour
• Sympatric speciation is common in plants (allo-
  and autoploidy), not so common in animals