A grouping of closely related genres "serving broadly similar communicative purposes, but not necessarily all the communicative purposes in cases where they serve more than one" (Bhatia, 2004, p. 59).
Bhatia, V. K. (2004). Worlds of Written Discourse. London: Continuum.
In book publishing, "promotional discourse" is enacted through its genre colony: a "constellation of several closely related genres with an overlapping communicative purpose of promoting a product or service to a potential customer" (e.g., "advertisements, promotional letters, and book blurbs," Bhatia, 2004, p.60).