Zeros are used when a new branch point needs to be inserted above a well-established branch point on the mitochondrial tree. One of the best-known examples of this is the insertion of R0 between the R and HV branches.

• R
  • R0 <–
    • HV

Note: In some older papers, the “pre” prefix is use instead of a zero. Thus, R0 was might be called pre-HV in these papers.