Cladistics Homework
Name: _________________________________
25 points
Due: Wed March 15
I STRONGLY RECOMMEND USING A PENCIL FOR THIS ASSIGNMENT!
1. (2 points) Consider the data displayed in the table below for a hypothetical group of
plants. Taxa 1-3 are your ingroup, whose relationship you are trying to resolve.
(A)
Leaves
Taxon 1
Taxon 2
Taxon 3
Outgroup
opposite
alternate
alternate
alternate
CHARACTERS AND CHARACTER STATES
(B)
(C)
(D)
(E)
Flower
Ovary
Fruit
Seed coat
Color
chambers
yellow
one
fleshy
smooth
yellow
two
fleshy
smooth
red
one
dry
rough
red
two
dry
rough
(F)
Seed
number
many
many
few
many
The first step in building a cladogram is to construct a character matrix. The
characteristics of the outgroup are set to 0. If a taxon shares the same character state as
the outgroup, then it is assigned a 0; if its character state is different from the outgroup, it
is assigned a 1. Fill out the character matrix below. Taxon 3’s character states have
already been filled in as an example.
(A)
Leaves
Taxon 1
Taxon 2
Taxon 3
Outgroup
CHARACTERS AND CHARACTER STATES
(B)
(C)
(D)
(E)
Flower
Ovary
Fruit
Seed coat
Color
chambers
0
0
0
0
1
0
0
0
0
0
(F)
Seed
number
1
0
2. (9 points) Once you have filled out the character matrix, draw the three possible
cladograms in the trees provided below. Indicate in each: a) the taxa names (1,2,3) on the
tips of the branches, b) hatch marks for the most parsimonious location where each trait
would evolve within that tree, and c) the total number of assumptions the tree makes.
O
O
O
# Assumptions: ________
# Assumptions: ________
# Assumptions: ________
4. (5 points) In the space below, redraw ONLY the most parsimonious tree of the three
you drew above, but using the other type of vertical cladogram used (with perpendicular
branches rather than diagonal branches; see picture below). Make sure you mark the
taxa and the character traits in the new tree, just like you did in the old one!
Example:
5. (2 points) What are two things you could do to make your cladogram more robust
(meaning to be more confident in the relationships you depicted)?
The following questions pertain to the cladogram drawn below. Note that the common
ancestor of all of these taxa exhibits traits ABCDE. The changed / derived forms of each
are indicated with an apostrophe (e.g. A’ is the derived form of character A). Answer the
questions that follow (1 point each).
6. Is E’ a plesiomorphic, apomorphic, or homoplasic character? __________________________
7. Is B’ an autapomorphic, synapomorphic, or plesiomorphic character? ____________________
8. Taxa with character A’ form a: monophyletic, paraphyletic, or polyphyletic clade? __________
9. Is C (not C’) an ancestral or derived character state?__________________________________
10. Let’s say that all organisms with character D (not D’) are grouped taxonomically. Do taxa
with character D comprise a monophyletic, polyphyletic, or paraphyletic group?______________
11. Let’s say that all organisms with character E’ are grouped taxonomically. Do these taxa
comprise a monophyletic, polyphyletic, or paraphyletic group?____________________________
12. Which taxa (1, 2, 3, and/or 4) possess the derived character state of trait B? ______________