Question

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?

Answer 1

I don’t have the insect character table or the cladogram you made, so I can’t give the numeric parsimony score or name the sister taxa yet. If you paste (or upload) the table of insects and character states, or a picture/screenshot of your CLADOGRAM tab, I will compute the lowest possible parsimony score and identify the two most closely related insects.

Below are clear steps I’ll follow (and you can follow too) so you know what to send and what I’ll do:

What I need from you
- The list of insects (taxa) used in the activity.
- The character matrix: for each insect, the state of each character (preferably 0/1 or presence/absence; if multistate, list the states).
- CSV, plain text table, or a screenshot/photo of your table is fine.

How I’ll find the lowest parsimony tree
1. Verify the character matrix and convert characters to discrete states (0/1).
2. If there are N taxa, I’ll consider candidate tree topologies (for small N I can examine all; for larger N I’ll use heuristic search).
3. For each candidate tree, I’ll compute the parsimony score using Fitch parsimony:
- For each character, work from tips toward the root:
- At each internal node, if the two child sets intersect, assign that intersection; if they don’t intersect, assign the union and add 1 step.
- The minimum number of state changes for that character is the number of unions you had to make while building the tree.
- Sum the steps for all characters to get the tree’s parsimony score.
4. Identify the tree(s) with the smallest total score — that’s the most parsimonious solution.
5. On that most-parsimonious tree, the two most closely related insects are the sister taxa that share the most recent common node (i.e., they form a pair that branches together without any other taxa between them).

Tips to reduce parsimony while building the tree in the CLADOGRAM tab
- Group taxa that share derived characters (shared 1s) together.
- Keep taxa with unique derived characters as separate branches (they will add steps).
- If two taxa differ only by one character, they are good candidates to be sister taxa.
- Try alternative branch swaps (NNI or SPR) until parsimony stops improving.

If you paste the matrix here I will:
- Build the most parsimonious tree(s),
- Report the lowest possible parsimony score,
- Identify the pair of most closely related insects,
- (Optionally) describe where any homoplasy (convergent changes) occurs.

Send the table or a picture and I’ll do the calculations.