+ \code{\link{corBrownian}}, \code{\link{corMartins}},
+ \code{\link{corGrafen}}, \code{\link{corPagel}},
+ \code{\link{corBlomberg}}
+}
+\examples{
+tr <- rtree(5)
+## all are the same:
+vcv(tr)
+vcv(corBrownian(1, tr))
+vcv(corPagel(1, tr))
+vcv(corPagel(0, tr))