Question

Question: How do you create parsimonious cladograms with more complex branching?
1. Build: As you did in activity A, use the information provided to fill in the table of
characteristics for insects. Check that your table is correct. On the CLADOGRAM tab, use
your table to create an insect cladogram. Make adjustments until you achieve the lowest
possible parsimony score, and then compare your cladogram to the accepted cladogram.
When you are done, take a snapshot of the cladogram and save it in your document.
What is the lowest possible parsimony score?
Which two insects are most closely related?
2. Build: Create cladograms for the Primates and Animals groups
(skip the Artiodactyla for now). These cladograms are a little
more complex, and you may have to include multiple branches
at the same level, such as in the example shown at the right.
When you have built cladograms with the lowest possible
parsimony score, compare them to the accepted cladogram.
Take snapshots of the finished cladograms and save them in your document.
3. Observe: Sometimes a trait can evolve separately in different groups. For example, both
bats and birds have wings, but their common ancestor did not have wings.
In the Animals cladogram, which trait evolved two different times?
4. Think and discuss: What could cause similar traits to evolve independently in different
species?

Answer 1

I can’t see your data or the interactive cladogram tool, so I can’t give the exact parsimony score or name the two insects from your table. Below are clear, practical steps you can follow to produce parsimonious cladograms with complex branching and to answer the specific questions in your activity.

1) How to build a parsimonious insect cladogram and find the lowest parsimony score
- Fill and verify the character matrix (rows = taxa, columns = characters, state = present/absent or coded states). Make sure there are no input errors.
- Put the taxa on the CLADOGRAM tab and arrange branching so that shared derived characters (synapomorphies) are grouped together.
- Compute the parsimony score: for each character, map where the state changes occur on your tree and count the number of changes; the total across all characters is the parsimony score. The software will usually calculate this automatically.
- To reduce the score, try rearranging branches (swap sibling subtrees, introduce polytomies where appropriate, move single taxa) to group taxa that share derived states. Each rearrangement can change how many times a character must change.
- Stop when no rearrangement lowers the total number of character-state changes: that is your lowest (most parsimonious) score.
- Which two insects are most closely related? Identify the pair of taxa that share the most recent common node (the sister taxa). The accepted cladogram you compare to will show which two are sister taxa if your tree is correct.

2) Creating more complex cladograms (Primates and Animals groups)
- Use the same parsimony principle but allow for multiple branches at the same level (polytomies) if your character matrix supports simultaneous splitting.
- When branching is more complex, try systematic rearrangements: move one taxon at a time, swap subtrees, and check the parsimony score after each change.
- Keep grouping taxa that share the same derived character states to minimize independent changes.
- When your score can’t be lowered, compare with the accepted cladogram and take snapshots.

3) How to tell if a trait evolved more than once (what to look for in the Animals cladogram)
- Map the trait onto the finished tree. If the trait is present in two (or more) separated clades but absent in their most recent common ancestor (i.e., you must invoke the trait appearing twice rather than inherited once), that is evidence it evolved independently (a homoplasy).
- In many standard “Animals” datasets the trait that evolved independently is flight/wings — birds and bats have wings but their common ancestor lacked wings. So a common example answer: the wing (flight) trait evolved two different times (convergent evolution) in the animals cladogram.

4) Why similar traits evolve independently (explanations for convergent/parallel evolution)
- Similar selective pressures and ecological niches favor similar functional solutions (e.g., flight is useful for escaping predators or accessing food).
- Similar environmental constraints produce similar adaptations (analogous structures).
- Developmental/genetic constraints can channel evolution toward the same solutions from different starting points.
- Parallel evolution: closely related lineages with similar genetic/developmental backgrounds evolve similar traits independently.
- Exaptation: an existing structure is co‑opted for a new function in different lineages.
- Homoplasy can also come from reversals (a trait lost then re‑evolved) or from simple chance calling.

Quick tips
- Let the software compute parsimony but always manually inspect mapped character changes to understand where homoplasies occur.
- When trees are equally parsimonious, look for additional data (more characters) or other information (molecular data, fossil constraints) to resolve ambiguous branching.
- Document each rearrangement attempt and the parsimony score so you can show how you reached the minimum.

If you want, paste your character table or a screenshot of your cladogram here and I’ll help compute the parsimony score, identify the sister taxa among your insects, and point out any traits that appear to have evolved more than once.