\begin{itemize}
\item With phylogenetic distances among species, e.g., $w_{ij} =
- 1/d_{ij}$, where $1/d_{ij}$ are distances measured on a tree.
+ 1/d_{ij}$, where $d_{ij}$ are distances measured on a tree.
\item With taxonomic levels where $w_{ij} = 1$ if species $i$ and $j$
belong to the same group, 0 otherwise.
\end{itemize}