Microbial Diversity Part 2: Reading Phylogenetic Trees
1. Introduction to Phylogeny:
Reading Phylogenetic
Trees
“Nothing in biology makes sense except in
the light of evolution”
T.H. Dobzhansky (1973)
Dr. Rachel Mackelprang
2. Introduction to phylogeny
•Phylogeny is a description of the evolutionary
history of relationships among organisms
•Portrayed in a diagram called a phylogenetic tree
•The Tree of Life refers to the concept that all living
organisms are related to one another through shared
ancestry
3. Phylogeny was central to Darwin’s work on natural
selection
“I think” tree
First published tree
On the Origin of Species
5. How to read a
phylogenetic
tree
This is the common ancestor to all
groups on the tree. It is called the
root
6. How to read a
phylogenetic
tree
This is the common ancestor to all
groups on the tree. It is called the
root
The splits in the branches are
called nodes and indicate a
division of one lineage into two.
7. How to read a
phylogenetic
tree
This is the common ancestor to all
groups on the tree. It is called the
root
The splits in the branches are
called nodes and indicate a
division of one lineage into two.
The positions of the
notes on the time
scale indicate the
times of the
corresponding
species event
10. Phylogenetic trees are simplifications of species
evolution
Speciation is the
process whereby one
species gives rise to two
descent species
If B and C are species
descended from A, then
the branching (splitting)
point represents the
speciation event
12. Phylogenetic trees are simplifications of species
evolution
Remove the complex
backboneA
B
C
13. Phylogenetic trees are simplifications of species
evolution
Now imagine the
process occurring at a
larger time scale.
Phylogenies are the
result of multiple
speciation events over
long periods of time
A
B
C
D
E
14. Phylogenetic trees are simplifications of species
evolution
Now imagine the
process occurring at a
larger time scale.
Phylogenies are the
result of multiple
speciation events over
long periods of time
A
B
C
D
E
15. Phylogenetic trees are simplifications of species
evolution
Remove the complex
backbone
A
B
C
D
E
28. Questions of relatedness
Both trees say the same thing. g and h share a more
recent common ancestor with each other than either
does with f Present
Past
29. Questions of relatedness
Both trees say the same thing. g and h share a more
recent common ancestor with each other than either
does with f Present
Past
Relative
relatedness of
taxa is a question
of how recently
they share
common ancestry
31. Kahoot question 1
a b c d e f g h abcdefgh
Do both of these trees show the same information?
32. Kahoot question 2
a b c d e f g h a b c d e f g h
Do both of these trees show the same information?
33. Kahoot question 3
a b c d e f g h a b c d e fgh
Do both of these trees show the same information?
34. Kahoot question 4
Is taxon e more closely related to d or to h?
Recall: Relative
relatedness of
taxa is a question
of how recently
they share
common ancestry
35. Kahoot question 5
Is taxon d more closely related to c or to f?
Recall: Relative
relatedness of
taxa is a question
of how recently
they share
common ancestry