This is a simplified wrapper for ape's vcv
function. Setting
the runtime option PCMBase.UsePCMVarForVCV to TRUE will switch to a
computation of the matrix using the function PCMVar
.
PCMTreeVCV(tree)
a phylo object
a N x N matrix. Assuming a BM model of evolution, this is a matrix in which element (i,j) is equal to the shared root-distance of the nodes i and j.