BIOL 339 Phylogenetics Exercise 1

BIOL 339 Phylogenetics Exercise 1

Name(s) _____________________________           BIOL 339 Fall 2020

          

             ______________________________           Date ___________________________

Phylogenetics Exercise 1

 

An important part of any modern course in evolution is experience with cladistics. Your instructor has already shown you cladograms of organisms. As you already know, a cladogram is a graphical representation of proposed branching pathways of evolution. Time is one of the axes on a proper cladogram; we shall put time on a vertical axis with ancient time at the bottom of the cladogram, and the present time at the top of the cladogram. The extant organisms will be shown across the top of the cladogram, at the end of the evolutionary pathway through which they evolved to their present status. The pathways shown have long-straight sections where evolutionary transitions occur over time; the building up of features along a straight pathway is called anagenesis. At certain points in time the evolutionary pathway undergoes a transition that causes a branch to form; this is called cladogenesis. At this branching point, one species diverged into two species. In cladistic analysis, we attempt to determine the pathway of evolution for a related group of organisms. The group of interest is called the ingroup; most cladograms also include a “nearest relative but not a member of the ingroup” organism which is called the outgroup. For this homework exercise you may work alone or in teams of two. A team may turn in a joint exercise for a joint grade.

 

 

 

Initial Classification

Find  Clade Critters Lacking Antennae on Page 9. Sort six of these species (OG, A, B, C, D, and E) into three groups. Ignore F for this part of our exercise. Your job as taxonomists is to identify feature(s) that differentiate the groups. In the table below, list the taxa belonging to each of your three groups and the feature(s) that unify the members of this group and distinguish them from members of the other two groups.

 

Members of this Group

The unifying/distinguishing feature(s)

 

 

 

 

 

 

 

Some taxonomists will group the Clade Critters in ways different from yours. And, if the feature selections unambiguously classify the organisms into distinct groups, then all of these organizing rules could potentially be defended as defining the taxonomy of Clade Critters. Of course the choices would then be quite subjective and thus not particularly useful! Modern taxonomy addresses this through cladistics.

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Cladistics with “Clade Critters”

You have noticed some of the features in the phenotype can help distinguish organisms. Use the images of the Clade Critters lacking antennae to construct a cladogram! To begin in a systematic and organized way, using the characteristics of the organisms, put together a data matrix of the characteristics you observe. Polarize the character states based upon the phenotype of the out-group (OG) critter; the condition shown in the out-group should be considered the plesiomorphic state, the apomorphic state will be an evolutionary change found among the members of the in-group (A, B, C, D, E). For each character, put 0 in the matrix for those taxa with the plesiomorphic state and a 1 in the matrix for those taxa with the apomorphic state. Note: width is different from length and thickness, so be careful naming your apomorphic states!

 

Body Part

Character

Apomorphic State

OG

A

B

C

D

E

1 Eye

size

 

 

 

 

 

 

 

2 Eye

color

 

 

 

 

 

 

 

3 Neck

width

 

 

 

 

 

 

 

4 Body

width

 

 

 

 

 

 

 

5 Body

color

 

 

 

 

 

 

 

6 Wing

width

 

 

 

 

 

 

 

7 Wing

length

 

 

 

 

 

 

 

8 Leg

length

 

 

 

 

 

 

 

9 Leg

thickness

 

 

 

 

 

 

 

10 Stinger

length

 

 

 

 

 

 

 

 

 

On this page you will construct a cladogram for A-E and the outgroup. Time is on the vertical axis of this page. The outgroup (OG) taxon is already placed as an extant species at the top of the cladogram. Its line of evolution is shown extending down the page to the bottom representing the common ancestor shared with the members of the ingroup (A-E). The apomophies (1-10) have evolved along pathways extending up and to the right of this common ancestor. Widely shared (synapomorphic) features evolved earlier in the branching pathways; unshared (autapomorphic) features evolved most recently. Using the concepts of parsimony (simplest solution) construct the rest of the cladogram for the 5 ingroup taxa of Clade Critters. Be sure to write in the numbers for the apomorphic character state transitions and draw small hash marks across the evolutionary path where the numbered transitions occur. 

 

OG

 

A Newly-Discovered Species!

A scientist has just found a new species of Clade Critter. We will need to revise our cladogram to include this new species: taxon F (page 9). You need not re-enter the character states for the other taxa from your matrix on the previous page, but you will need to add the new column for species F.

 

Part

Character

Apomorphic State

OG

A

B

C

D

E

F

1 Eye

size

 

 

 

 

 

 

 

 

2 Eye

color

 

 

 

 

 

 

 

 

3 Neck

width

 

 

 

 

 

 

 

 

4 Body

width

 

 

 

 

 

 

 

 

5 Body

color

 

 

 

 

 

 

 

 

6 Wing

width

 

 

 

 

 

 

 

 

7 Wing

length

 

 

 

 

 

 

 

 

8 Leg

length

 

 

 

 

 

 

 

 

9 Leg

thickness

 

 

 

 

 

 

 

 

10 Stinger

length

 

 

 

 

 

 

 

 

 

 

Using the concepts of parsimony and synapomorphy in the space below, revise your earlier cladogram by adding F. Be sure to write in the numbers for the apomorphic character state transitions and, draw small hash marks across the evolutionary path where the transitions occur.  Use a straight-edge. .

Circle one homoplasy. The homoplasious character is_____________ .

Explain why this character is a homoplasy.

 

 

The Final Example

The final set of Clade Critters to decipher is on page 10. These larger critters have antennae and are not closely elated to the Clade Critters you used previously. .

 

Part

Character

Apomorphic State

OG’

A’

B’

C’

D’

E’

Antenna

 

 

 

 

 

 

 

 

Antenna

 

 

 

 

 

 

 

 

Body

 

 

 

 

 

 

 

 

Body

 

 

 

 

 

 

 

 

Stinger

 

 

 

 

 

 

 

 

 

Using the concepts of parsimony and synapomorphy in the space below, construct the most parsimonious cladogram for the clade critters with antennae. Be sure to write in the apomorphic character state names (do not number them!) and draw small hash marks across the evolutionary path where the character state changes. Circle any homoplasies.

Write a short comment explaining why this is the most parsimonious cladogram.

 

 

 

 

 

 

 

One homoplasious character is____________________________ .

Explain why this is a homoplasy.

 

Clade Critters Lacking Antennae

Newly Discovered Species(ignore until page 3) 

Clade Critters Having Antennae