morphospace

1
(No Transcript)
2
time
morphospace
3
time
morphospace
4
synapomorphy
Example Feathers among vertebrate groups
5
Everyone has the character
It is primitive in the phylogeny
Shared-primitive character
Symplesiomorphy
Example The number of limbs in terrestrial
vertebrates
6
How do you tell if a trait is primitive or
derived?
Outgroup
7
Principle of Parsimony Simpler explanation is
more likely
Parsimony -- topology that minimizes total
evolutionary change
8
(No Transcript)
9
(No Transcript)
10
How to Construct Trees?
Need characters morphological mtDNA, cpDNA
-- genera, species nuclear DNA -- classes,
families, orders, genera rRNA -- kingdoms,
phyla, classes
Need a method for using the characters
11
abcdefg abcdefg
abcdefg abcdefg
A B C D
A B C D
12
abcdefg abcdefg
abcdefg abcdefg
A B C D
A B C D
a is shared ancestral
a a
13
abcdefg abcdefg
abcdefg abcdefg
A B C D
A B C D
b b
c c
a is shared ancestral b and c are shared
derived d e f and g are uninformative
a a
14
(No Transcript)
15
(No Transcript)
16
v
v
17
C
B
A
C
A
B
3 species -- 3 possible trees 3 known, plus 4th
-- 15 possible trees 3 known, plus 10 --
282,137,824 possible trees plus 20 -- gtgt81023
18
How to find the best tree?
Sample 1000 trees find the best and search near
them avoid characteristics of the worst trees
Break it up into smaller groups that can be
searched, then combine groups, forcing your
search to areas that maintain the branching you
find in
Add one at a time
Algorithmic--searching for the best method for
finding the tree
19
Maximum liklihood methods
Starts with a model of evolutionary change e.g.
All base pair changes equally likely
Transitions more likely than transversions 3rd
base pair changes more likely than 1st base pair
changes Synonymous changes more likely than
non-synonymous changes
Rules that imply probability
Calculate the probability that a particular
change occurred The tree that has the highest
probability (i.e liklihood) is favored
20
Using Molecular Data
Small number of character states (A,T, G, C)
Reversions A ? G ? A will be frequent
What do you do with mistakes?
Homoplasy
21
(No Transcript)
22
How good is a method (e.g. parsimony) at
uncovering the phylogeny?
23
Consider 4 taxa, trait is one codon 1.
GAA 2. GAA 3. GAT 4. GAT
24
(No Transcript)
25
Types of characters morphological mtDNA, cpDNA
-- genera, species nuclear DNA -- families,
orders, genera rRNA -- phyla,
classes Considerations informative characters
-- shared derived traits direction of change
-- outgroup problems -- convergence, parallel
evolution, reversal Methods parsimony maximum
likelihood, etc.
26
What is the relation of systematics to
classification?
Monophyletic Paraphyletic
Polyphyletic all descendents of
some, but not all, shared character
common ancestor descendents
not present in possess trait possess
trait common ancestor
27
Classification that does not reflect history is
uninformative and misleading. It may lead to
mistakes--certainly it is wrong
28
(No Transcript)
29
Uses of phylogenies rates of evolutionary
change -- Hawaiian honeycreepers patterns of
adaptive evolution -- hammerhead
sharks classify diversity
http//tolweb.org/tree/phylogeny.html coevolutio
n and cospeciation -- hosts and
parasites comparative method
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
Sequence of character change Evolution of
hammerhead sharks Two hypothesized
functions - bowplane to increase
lift while swimming - enhanced orientation
and prey detection Martin 1997 Nature
364494 921 bp mtDNA eight hammerhead
taxa plus outgroup
35
(No Transcript)
36
(No Transcript)
37
Gopher and louse phylogenies are significantly
congruent
pocket gophers lice
38
The timing of diversification is significantly
correlated in gophers and lice
39
Phylogenies congruent!! but, are they?
40
(No Transcript)
41
Cyphomyrmex
Myrmecocrypta
Mycocepurus
42
A phylogeny represents the evolutionary history
of a lineage in terms in terms of when splits
arose and how much descendant taxa differ from
the ancestor Molecular sequence data have
revolutionized the construction of phylogenies
because they provide large numbers of
simple characters Phylogenies are based on
shared derived characters ancestral vs. derived
state is determined by comparison to an
outgroup Parsimony is the most frequently used
method for constructing phylogenies, but it may
produce multiple equally parsimonious trees,
especially if the number of taxa is large Robust
phylogenies based on molecular data enable
evolutionary biologists to address several
types of questions