Evolutionary Tree

[SteveII]

Sorry, it is very much a component. It is assumed in just about every evolutionary experiment and conclusion every reached. Show me one area it is not assumed and would therefore not be detrimental to the theory if it were found to be incorrect.

Give an example where universal common descent was a necessary component of an evolutionary experiment. You're making a claim about necessary assumptions, you support it.

The study of fossils assumes everything biological is related and attempts to chart them accordingly.
The study of genetic mutation rates assumes everything is related and therefore rates of changes can be measured going back.
The study of parallel and convergent traits assumes (be definition) that a common ancestor did not have the traits being studied. 
The study of biological systems assumes everything is related so compares different systems in different species to find similarities to establish potential building blocks that could have evolved.

I could go on...but the point is that if common decent is disproved, there are ramifications in every sub-field--and many existing conclusions would have to be thrown out or at the very least, reexamined.