I doubt you're still interested, but just in case...

The author of the package mentions:

"For these data, spatial connectivity is best defined as the overlap between home ranges of individuals, modelled as disks with a radius of 1150m"

Therefore: d2=2300 (http://adegenet.r-forge.r-project.org/files/tutorial-spca.pdf ).

Of course, besides having an idea of these gastropods dispersion, you need your coordinates to have a reference system in order to set a maximum distance (measured in meters) between points.

You could just change the connection network from type 5 to type 1, delete d1 and d2. That creates a Delaunay connection network.