Which evidence least changes a phylogenetic tree?

Which type of evidence is least likely to result in changes to a phylogenetic tree?

A. DNA sequencing

B. Fossil record

C. Discovery of new species

D. Physical characteristics

Ans: The evidence most unlikely to change a phylogenetic tree is D. Physical characteristics (i.e., morphological traits). 

Here's why: 

Molecular data (DNA sequencing) provides incredibly detailed, objective information about genetic relationships. Once you get enough new or improved sequence data, it often leads to a revision of existing trees. 

The fossil record provides information about ancestral forms or relevant transition forms, which could lead to a rethinking of ancestor and branching orders. 

Finding a new species has the possibility of adding new taxa to the existing tree, which may lead to new rearrangements or new branches based on the DNA sequence or morphology of the new species. 

Because physical characteristics (morphology) are more prone to convergent evolution (different lineages evolving similar features independently) or phenotypic plasticity, they are more misdirected regarding actual evolutionary relationships. Consequently, a morphological trait, being measurable (exact) or an observation (more vague), is usually less directed or precise than molecular evidence. Any new observable morphological traits or characteristics are not as likely to change well-established phylogenetic trees.

Thus, among the options, physical characteristics is the best answer.