The 'wikisphere' is made up of all wikis, and any interconnections between them. Wikis can influence, and may be influenced by one another; by borrowing their content, migration or sharing of their active users, documenting and critiquing their activities, serving as homes for refugees and exiles from other wikis, etc.
Scopes of 'community'
On a vast wiki like the English Wikipedia, a virtual community can form around one page or one subject they are all interested in; write about, edit, discuss. Like a page about a City, real communities form virtual communities and vice versa. Naturally, a bigger scope of wiki community are the active users of one wiki. Beyond that, there are wiki farms like Referata, breeding places for initially mostly small wikis where the founder gets support from the community of the farm, synergies are established like the Volunteer Spam Task Force on Wikia where the individual wikis are not so individual, rather like offices in a big building and you need only one user account to access them all. Others prefer to call one server for the development for many wikis a hive like in 'bee hive' which is a charming analogy like anthill that illustrates the business of folks there but does not reflect that there is no 'queen'.
The Wikisphere after all is the entirety of independent individuals and their colaborations which kind of culminates or confluences in this comparatively small wiki where it's community endeavours to build a dynamic hub for the multi-language, international and increasingly complex Wikisphere.