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# Complete tree phylogenetic beta-diversity measure

The unweighted complete tree (CT) measure calculates the dissimilarity between a pair of communities by considering the amount of shared, unique, and external branch length within a tree spanning *all* sequences from *all* communities. It is an unweighted or qualitative measure as only the presence or absence of a sequence is considered. This calculator can be used with the phylo.betadiversity command. The dissimilarity between communities *i* and *j* is given by:

<math>D_{CT} = \frac{b+c}{a^*+b+c+d}</math>

where,

<math>a^*</math> = the amount of branch length shared by the two communities within the CL subtree.

<math>b</math> = the amount of branch length unique to community *i*.

<math>c</math> = the amount of branch length unique to community *j*.

<math>d</math> = the amount of branch length external to communities *i* and *j*.

### Mathematical properties

### Points-of-interest

### Further information

Parks, DH and Beiko, RG. (2011). **Quantifying phylogenetic β-diversity over rooted and unrooted trees**. (in preparation)