int ext_nodes = _phylogeny.getRoot().getNumberOfExternalNodes();
final int max_depth = PhylogenyMethods.calculateMaxDepth( _phylogeny );
if ( ext_nodes == 1 ) {
int ext_nodes = _phylogeny.getRoot().getNumberOfExternalNodes();
final int max_depth = PhylogenyMethods.calculateMaxDepth( _phylogeny );
if ( ext_nodes == 1 ) {