This function implements the SDM method of Criscuolo et al. (2006) for a set of n distance matrices.
SDM(...)a 2-element list containing a distance matrix labelled by the union of the set of taxa of the input distance matrices, and a variance matrix associated to the returned distance matrix.
2n elements (with n > 1), the first n elements are the
    distance matrices: these can be (symmetric) matrices, objects of
    class "dist", or a mix of both. The next n elements are the
    sequence length from which the matrices have been estimated (can be
    seen as a degree of confidence in matrices).
Andrei Popescu
Reconstructs a consensus distance matrix from a set of input distance
  matrices on overlapping sets of taxa. Potentially missing values in
  the supermatrix are represented by NA. An error is returned if
  the input distance matrices can not resolve to a consensus matrix.
Criscuolo, A., Berry, V., Douzery, E. J. P. , and Gascuel, O. (2006) SDM: A fast distance-based approach for (super)tree building in phylogenomics. Systematic Biology, 55, 740--755.
bionj, fastme, njs,
  mvrs, triangMtd