mrca returns for each pair of tips (and nodes) its most
recent common ancestor (MRCA).
getMRCA returns the MRCA of two or more tips.
mrca(phy, full = FALSE)
getMRCA(phy, tip)a matrix of mode numeric (mrca) or a single numeric value
(getMRCA).
an object of class "phylo".
a logical indicating whether to return the MRCAs among
all tips and nodes (if TRUE); the default is to return only
the MRCAs among tips.
a vector of mode numeric or character specifying the tips; can also be node numbers.
Emmanuel Paradis, Klaus Schliep, Joseph W. Brown
For mrca, the diagonal is set to the number of the tips (and
nodes if full = TRUE). If full = FALSE, the colnames and
rownames are set with the tip labels of the tree; otherwise the
numbers are given as names.
For getMRCA, if tip is of length one or zero then
NULL is returned.