neighbour patches

Hi,

I am tempted to dig in graph theory and analyse connections between 
discrete landscape patches. Re-reading 'Applied Spatial Data Analysis 
with R' I was happy to find basics chapter 9. However, it reports on 
graphs where (euclidian) distance is computed between patch centroids.

Does anybody have an idea about strategies or packages permitting to use 
the shortest distance between patch borders instead (which is more 
realistic with regard to animal movement) ?

Patrick