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The Origin of Species: Lizards
in an Evolutionary Tree

Educator Materials

USING DNA TO EXPLORE LIZARD PHYLOGENY
OVERVIEW
This lesson serves as a supplement to the film Lizards in an Evolutionary Tree
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They have evolved to
occupy different niches in the environment, and studying them is giving researchers surprising insights into
evolutionary processes, such as adaptation by natural selection, convergent evolution, and the formation of new
species
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In Part 1, students
examine the diverse appearance of the lizards and group them into categories according to different body types
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In Part 2, mitochondrial DNA sequence data from these same species of lizards are used to
generate a phylogenetic tree to reveal their true evolutionary relationships
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Students watch
the film in stages at different points in the activity
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Adaptive radiation occurs when an ancestral species diversifies into many descendant species that occupy
different environmental niches
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DNA sequence comparisons among different populations and species allow scientists to determine the
degree of relatedness of different species
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CURRICULUM CONNECTIONS
Curriculum
NGSS (April 2013)
AP Biology (2012–13)
IB Biology (2015)

Standards
MS-LS1-5, MS-LS4-2, MS-LS4-4, MS-LS4
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B, MS-LS4
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A, HS-LS4
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C
1
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1, 1
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2, 1
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4, 1
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2, 1
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1, 1
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2, 1
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3
4
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1, 5
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4, C
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BioInteractive
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Allow for more time if you need to cover basics of DNA alignment in greater detail
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MATERIALS
•
•
•
•

A set of lizard cards that accompanies this document
Access to a computer that is connected to the Internet
HHMI Short Film Lizards in an Evolutionary Tree
(Optional) A computer with the freely available ClustalX program installed

BACKGROUND SUMMARY
This section provides a brief summary
...
hhmi
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pdf)
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Caribbean islands are home to
the anoles
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(Reproduced with permission from
Losos, J
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UC Press, 2009
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The groups are referred to as ecological morphotypes, or
ecomorphs
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The
film discusses only four ecomorphs: the crown-giant, trunk-ground, twig, and grass-bush anoles
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Published March 2014
Updated April 2015, May 2017
www
...
org

Page 2 of 10

The Origin of Species: Lizards
Educator Materials

in an Evolutionary Tree
Table 1
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(See Figure 2 for an illustration of
the habitats of different ecomorphs
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The long-legged adaptation helps them not only catch prey on
the ground but also avoid predators
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The grass-bush anoles are small and have long legs and strikingly long
tails that help them balance on thin branches and blades of grass, and the trunk-crown anoles, with their large
toe pads, are adapted to living on leaf surfaces in the canopy
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Anoles occupy a variety of
ecological niches
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The
figure shows the six ecomorphs of anole
lizards found in the Caribbean islands in
their habitats
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Lizards in an
Evolutionary Tree
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)

Published March 2014
Updated April 2015, May 2017
www
...
org

Page 3 of 10

The Origin of Species: Lizards
in an Evolutionary Tree

Educator Materials

Convergent Evolution Among Anole Lizards
There are different explanations for why similar ecomorph classes can be found on each of the different islands
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Under this scenario, one possibility is that the islands were contiguous in the past
when the ecomorphs evolved, and subsequent plate tectonics separated the islands
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In these scenarios, you would predict that DNA analysis would reveal, for
example, that the twig anole species on all of the islands are more closely related to one another than they are
to the grass-bush, trunk-ground, or trunk-crown anoles on the same island
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A
prediction based on this hypothesis is that the anoles on each island would be more closely related to one
another than they would be to species on other islands belonging to their ecomorph
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This suggests that the same adaptations evolved independently in
different anole populations on each of the islands, an example of convergent evolution
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A student worksheet is provided to guide the activity, but, as explained below, there are points at
which you may wish to stop and conduct a whole group discussion, show the film to the whole class, or explain a
concept
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PART 1: Identifying the Ecomorphs and Exploring Anole Adaptive Radiation
At this point, students have not seen the film Lizards in an Evolutionary Tree yet
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Hand out the student worksheet for Part 1 and a set of lizard cards to each group
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Students can use any clues in the photographs to group the lizards as they see fit
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They may even group
them by the habitat pictured, such as branches, tree trunks, or grass
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Allow students time to answer Question 1, then ask the teams to explain how they grouped the lizards and
their rationale for the various groupings
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3
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4
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5
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The 16 species represent the following four ecomorphs
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Also, the first page of the lizard picture file can be used as a master reference
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BioInteractive
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Allow students time to answer Questions 3–6
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For example, the large toe pads
of the trunk-crown anoles allow them to adhere to leaves and move about freely among the leaves of the tree
canopy
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Refer to the “Different
Morphologies of Anole Lizards” section in the background
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PART 2: Generating a Phylogeny from DNA Sequences and Revealing Evolutionary Relationships of Anoles
1
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Follow the procedure outlined in Sequence Alignment Introduction Using ClustalX:
http://media
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org/biointeractive/activities/lizard/Sequence-Alignment-Introduction
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Have your students explore the Click and Learn Creating Phylogenetic Trees from DNA Sequences:
http://www
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org/biointeractive/creating-phylogenetic-trees-dna-sequences
2
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Have students follow the directions to download the Anolis sequences text file and then use www
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fr
to align the sequences and create a phylogenetic tree
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The website will generate a phylogenetic tree that can be saved in a variety of formats
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Figure 3
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phylogeny
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Students’ phylogeny
should be similar,
but there may be
small differences
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BioInteractive
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The red numbers in the phylogeny result are bootstrapping values and denote how confident the program is
about the specific branch pattern
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Values less
than 0
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However, because the purpose of this activity is to illustrate the
principle of DNA sequence comparison, students should not worry about it too much
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Print out two copies of the students’ phylogenetic tree per group of students and hand out the rest of the
student handout
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Have them use the list of lizard species to color the trees in the following ways:
a
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If
both branches at a node are the same color, color the root branch and continue left to the next node
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On the other copy, color each branch similarly according to the ecomorph
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Allow students time to examine the phylogenetic trees and answer Questions 1–6
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8
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Discuss as a class
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Students may ask whether convergent evolution occurs in groups other than the anoles
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They could list tuna, dolphins, manatees,
and ichthyosaurs
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Reduced or absent
limbs is another: snakes, caecilians, sirens, slow worms, worm lizards
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(Optional) Refer to the reference-phylogeny figure at the end of this lesson
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Find the 16 species used in this activity and see if their phylogeny differs from
the tree generated by the student groups
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Published March 2014
Updated April 2015, May 2017
www
...
org

Page 6 of 10

The Origin of Species: Lizards
in an Evolutionary Tree
List of Lizard Species
Species name

Island

Ecomorph

Anolis alutaceus

Cuba

Grass-bush

Anolis angusticeps

Cuba

Twig

Anolis chlorocyanus

Hispaniola

Trunk-crown

Anolis cristatellus

Puerto Rico

Trunk-ground

Anolis cybotes

Hispaniola

Trunk-ground

Anolis evermanni

Puerto Rico

Trunk-crown

Anolis grahami

Jamaica

Trunk-crown

Anolis lineatopus

Jamaica

Trunk-ground

Anolis occultus

Puerto Rico

Twig

Anolis olssoni

Hispaniola

Grass-bush

Anolis ophiolepis

Cuba

Grass-bush

Anolis porcatus

Cuba

Trunk-crown

Anolis pulchellus

Puerto Rico

Grass-bush

Anolis sagrei

Cuba

Trunk-ground

Anolis sheplani

Hispaniola

Twig

Anolis valencienni

Jamaica

Twig

Leiocephalus barahonensis

Educator Materials

Outgroup

ANSWERS
PART 1: Identifying Ecomorphs and Exploring Anole Adaptive Radiation
For Questions 1–4, student answers will vary
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5
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Adaptive radiation occurs when an ancestral species diversifies into many descendant species that occupy
different environmental niches
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6
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Student answers will vary
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Published March 2014
Updated April 2015, May 2017
www
...
org

Page 7 of 10

The Origin of Species: Lizards
in an Evolutionary Tree

Educator Materials

PART 2: Generating a Phylogeny from DNA Sequences and Revealing Evolutionary Relationships of Anoles
1
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Colored by island:

Figure 4
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Red = Cuba, Green =
Jamaica, Blue = Puerto
Rico, Yellow = Hispaniola
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Species from
Cuba are more divided but
still show some clustering
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Colored by ecomorph:
Figure 5
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Red = Trunk-ground, Green
= Trunk-crown, Blue =
Grass-bush, Yellow = Twig
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In general, when you look at species colored by islands, they seem to cluster together
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The Cuban and Hispaniola
species also cluster, but the pattern is more complicated
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2
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Different ecomorphs are grouped together on branches
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Published March 2014
Updated April 2015, May 2017
www
...
org

Page 8 of 10

The Origin of Species: Lizards
in an Evolutionary Tree

Educator Materials

3
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All species from Jamaica cluster together, and many species from Puerto Rico cluster together
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4
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Justify your claim
with several pieces of evidence from the colored phylogenetic trees
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5
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One hypothesis is that each ecomorph evolved once, and
the species belonging to the same ecomorph are closely related to one another
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Which hypothesis is supported by
the DNA analysis shown in the tree? Justify your answer and explain your reasoning
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This finding supports the hypothesis that most of the lizards on each island
evolved independently, in a process of convergent evolution, although there are exceptions
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Examine the relationship between Anolis sheplani and Anolis angusticeps
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Develop a possible hypothesis that could explain this
relationship
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Student answers will vary, but one could hypothesize
that A
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7
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Identify and explain any similarities and differences between the phylogeny shown
in the film and the phylogeny you made in this activity
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The film explains that species on an island
are more closely related to one another than to species belonging to the same ecomorph on other islands
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The general picture is the same, but some cases (see Question 6)
don’t fit
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RELATED CLASSROOM RESOURCES
Other Resources for the Film (http://www
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org/biointeractive/origin-species-lizards-evolutionary-tree)
Check this page to see other resources developed for the film
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hhmi
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Classroom Activities: Biodiversity and Evolutionary Trees (http://www
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org/biointeractive/biodiversityand-evolutionary-trees)
This is a companion classroom resource to accompany the Click and Learn above
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BioInteractive
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In the seashell activity, phylogeny generated by examining
morphology closely aligns with that generated from DNA, so it is a good contrast to the case of the anole lizards,
in which the two do not agree
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hhmi
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REFERENCES
Losos, J
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Lizards in an Evolutionary Tree
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Rabosky, D
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, and Glor, R
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(2010)
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PNAS 107, 2217–22183
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A
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, Brown, N
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, Chenna, R
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A
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, Valentin, F
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M
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, Lopez, R
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D
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J
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G
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Clustal W and Clustal X
version 2
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Bioinformatics 23, 2947–2948
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fr: Dereeper, A
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, Blanc, G
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, Buffet, S
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, Dufayard, J
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, Guindon, S
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, Lescot, M
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M
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(2008)
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fr: Robust phylogenetic analysis for the nonspecialist
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2008 Jul 1; 36 (Web Server issue): W465-9
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AUTHORS
Written by Satoshi Amagai, PhD, HHMI
Student Worksheet created by Valerie May, Woodstock Academy; Ann Brokaw, Rocky River High School; Susan Dodge,
consultant
Edited by Laura Bonetta, PhD, HHMI; Laura Helft, PhD, HHMI; copyedited by Linda Felaco
Reviewed by Jonathan Losos, PhD, Harvard University

Published March 2014
Updated April 2015, May 2017
www
...
org

Page 10 of 10

Fig
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Maximum clade credibility (MCC) tree resulting from BEAST analyses
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95; gray, 0
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70; white, pp < 0
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Island occupancy is indicated
across the tips of the tree (red, Cuba; blue, Hispaniola; orange, Puerto Rico; purple, Jamaica)
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Rabosky and Glor www
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org/cgi/content/short/1007606107

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