I would like to draw minimum spanning trees of a bunch of sequences. Some sequences are in multiple copies so I would like this to be represented as proportional circles. I am aware of the costly Bionumerics (Applied maths, Belgium) that does what I want see this but I want something free. I am also aware of mst in the ape library of R, spantree in the vegan library and minimum.spanning.tree in the igraph library but none of these let me specify the size of the circle according to number of sequence copies.
I was looking for a distance based approach but thank you for the suggestion.