# 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:

$D_{CT} = \frac{b+c}{a^*+b+c+d}$

where,

$a^*$ = the amount of branch length shared by the two communities within the CL subtree.

$b$ = the amount of branch length unique to community i.

$c$ = the amount of branch length unique to community j.

$d$ = the amount of branch length external to communities i and j.

### Further information

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