Workshop: Biosystematics

Figure 2. Phenogram of Caminalcules clustered in the sample exercise.
Note again that the similarity values assigned in the example were subjective. Different relative
similarities might have been assigned by a different observer. A phenogram provides a visual
representation of similarity relationships of OTUs, and nothing more. Note that clusters can be
rotated around their branches without changing the implied similarity relationships. For example, if
the diagram were rotated at the 0.3 branch point so that OTUs 2 and 7 were on the right, and OTUs
1, 3, 4, 5, 6 and 8 on the left, the information in the diagram would not be changed. The same would
be true of rotation at any branch point.
Given the computational tedium of working through this simple 8 OTU example, you can see
why real numerical taxonomic studies, which often involve large numbers of OTUs, require the use
of computers.