The three clusters are different logical groups. The Tomcat cluster grouping is handling session replication. The DefaultPartition cluster handles core clustering including HA-JNDI. Any TreeCache related clusters are handling replicated TreeCache instances.
These clusters all use JGroups internally and they are differentiated by cluster name, multicast address and port. Currently separate configurations are required for each cluster. The forthcoming JGroups 2.3 release will allow multiplexing of cluster configurations in cases where cluster groups are able to share configurations (e.g., JGroups stacks).
If you are running multiple partitions in a cluster, you need to distinguish them via the name, address and port settings. This is true for all of the clusters in your topology (e.g., Tomcat, TreeCache).