No attempt was made to assign branch lengths between the partial sequences and the rest of the tree.

For each species group, branch lengths were averaged to produce the trees shown (Figure 2).

However, this also makes the ancestor's branch length longer so that the root is unaffected.

Within a species, the branch length is also a measure of genetic diversity.

However, there are infinitely many other trees that differ from the three chosen ones only by differences in branch lengths.

Sometimes a branch length is measured in terms of geological years.

Because some species evolve at faster rates than others, these two measures of branch length are not always in direct proportion.

Start with a V shape until desired branch length is attained but lower branches to the bottom wire by autumn of the first year.

When branch length, ν, is measured in the expected number of changes per site then:

The branch lengths of trees follow an exponential distribution.