Treethinking

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Tree-thinking

• An introduction to phylogenetics

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Layers of Darwinism

• Descent from common ancestry (phylogeny)
• Descent with modification (change)
• Change in the genetic composition of populations
• Adaptation due to natural selection

3
Genealogical structures

• Phylogeny
• A depiction of the ancestry relations between
  species
• Tree-like (divergent)
• Pedigree
• A depiction of the ancestry relations within
  populations
• Net-like (reticulating)

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Four butterflies connected to their parents
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future
Individuals
past
Population
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Population
Lineage/ Species
What happened here?
Phylogeny
7
What happened here?
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Representation of phylogenies?
A
B
C
A
B
C
A simplified representation
The True History
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Some terms used to describe a phylogenetic tree
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Time
A
B
C
D
e
f
g
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Relatedness recency of common ancestry

• You are more closely related to your first
  cousins than your second cousins because.
• You are more closely related to a chimpanzee than
  to a worm because.

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Fish
Newt
Lizard
Mouse
Human
Is a newt more closely related to a fish or a
human?
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Fish
Newt
Lizard
Mouse
Human

• This is not how evolution happened
• All these species are alive today
• The order along the top can change without
  changing the content of the tree

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Now, is a newt more closely related to a fish or
a human?
Fish
Newt
Lizard
Mouse
Human
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Now, is a newt more closely related to a fish or
a human?
Fish
Newt
Lizard
Mouse
Human
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Which of the following is different?
A
B
C
D
E
A
B
C
D
E
A
B
A
B
C
D
E
E
D
C
A
B
C
D
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Fish
Newt
Lizard
Mouse
Human
Is a newt more closely related to a lizard or a
human?
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Relationships apply only to the tips that are
included
sparrow
mouse
kangaroo
caiman
crocodile
ostrich
Archaeopteryx
It does not matter that many species are left off
the diagram
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Which is false?
maize
oak
human
chimp
snake
moss
rice
fish
monkey
lizard
A
B
frog
mouse
bird
apple
fern
shark
newt
bird
E.coli
Bacillus
C
D
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A tree can depict uncertainty
moss
rice
mushroom
fly
monkey
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Why are phylogenies useful

• Allow one to infer
• Provide the basis for
• More

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How do we use trees to reconstruct history?
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Sometimes the reconstruction is
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Even when unambiguous, an inference can be..
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Diverse evolutionary events can be mapped onto
trees
A
B
C
D
E
Bird pollinated
Pink sap
20 Ma
Round leaves
10 Ma
Red petals
Alkaloids
25 Ma
Africa
Trees
35 Ma
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Biological classification

• All species are arranged in a hierarchical
  classification of
• In order to reflect phylogeny, we only recognize
  taxa that are

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The basic unit of classification
Corn
Moss
Clubmoss
Fern
Horsetail
Pine
Archaeopteris
A clade
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_____________ group Some members are more
closely related to organisms outside the group

• _________ group
• (______)
• Members are more closely related to each other
  than to any organisms outside the group

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Major Points

• ..
• ..