vcv is a single matrix, instead of a list of matrices, sim.corrs will simulate multivariate BM with a single rate matrix.
sim.corrs(tree, vcv, anc=NULL, internal=FALSE)n species in the tree (and nodes if internal=TRUE).
Revell, L. J. (2012) phytools: An R package for phylogenetic comparative biology (and other things). Methods Ecol. Evol., 3, 217-223.
fastBM, make.simmap, read.simmap, sim.history, sim.rates