As we saw in lecture the minimum evolution method parsimony

As we saw in lecture, the minimum evolution method (parsimony) worked well for reconstructing the ancestry of Y chromosomes carried by men from different parts of the world. Explain why the method would likely be less useful for reconstructing ancestry of (for example) the major animal phyla. What assumptions does the minimum evolution method require that would likely be violated in this case? What would be a better method? (You can assume that it is possible to find DNA sequences that are alignable among the phyla). Traditionally, deer, pigs, camels and other ungulates that walk on two toes have been placed in the order Artiodactyla, and whales and dolphins have been placed in a separate order, Cetacea. Based on information from lecture, is Artiodactyla monophyletic, paraphyletic, or polyphyletic? Explain. Answer the same question for the hypothetical example about blind salamanders given in lecture, supposing that the two blind species had been placed in their own genus based on their shared traits of white skin and lack of eyes. Explain your reasoning.

Solution

7)

In the Minimum Evolution method, the tree with the smallest sum of branch length is said to be optimal and are most likely to be the true one, minimum evolution is calculated from the distance matrix.

The construction of a minimum evolution tree is time-consuming because, the number of possible topologies rapidly increases with the number of taxa so it becomes very difficult to examine all topologies.

So this method is not useful for reconstructing ancestry of the major animal phyla as number of topologies is so large.

Genetically related species share same nucleotide at the same position is the assumption which is getting violated in this case.

Distance matrices can also be used to reconstruct ancestry of major animal phyla.

8)

a)

Artiodactyla is a paraphyletic taxon because it includes animals descended from a common ancestor, but does not include all its descendants.

b)

It might be an example of paraphyletic in which a group of organisms descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.