Would someone be able to point me to a generalisation of the Fitch algorithm to calculate parsimonious length for a topology, but which works for non-binary trees?

Actually our goal is to calculate consistency index correctly, in the face of (possibly) ambiguous DNA base symbols (R, Y, S, V, M, etc).

Getting consistency index involves knowing the minimum conceivable length of a tree, calculated for each character individually.

This part of the problem seems equivalent to calculating tree length, for each character separately, for a ‘bush’ topology in which all terminals are connected directly to the root.

I’m just not quite sure how to do that. But I’m sure it is known, in general.

Thanks a lot,

Daniel