This command allows you to specify a user tree. The user tree can then be used as a starting tree for a MCMC analysis. The format for the command is
usertree = <tree in Newick format>
For example,
usertree = (A,B,(C,D))
specifies an unrooted tree of four species. Note that the program requires that trees are binary (i.e., strictly bifurcating). Hence, there can be only one three-way split, as shown in the example. If the tree is not binary, the program will return an error.