$$V_{ij} = \gamma \times t_a$$
where $ta$ is the distance on the phylogeny between the root and the most recent common ancestor of taxa $i$ and $j$ and $gamma$ is a constant.
corBrownian(value=1, phy, form=~1)
"coef"(object, unconstrained = TRUE, ...)
"corMatrix"(object, covariate = getCovariate(object), corr = TRUE, ...)phylo representing the phylogeny
(with branch lengths) to considercorBrowniancorBrownian, or the coefficient from an
object of this class (actually sends numeric(0)), or the
correlation matrix of an initialized object of this class.
Martins, E. P. and Hansen, T. F. (1997) Phylogenies and the comparative method: a general approach to incorporating phylogenetic information into the analysis of interspecific data. American Naturalist, 149, 646--667.
corClasses