A loosely defined group of species. Zoology: "Aggregate - a group of species, other than a subgenus, within a genus. An aggregate may be denoted by a group name
interpolated in parentheses." -- The Berlin/MoreTax model notes: "[these] aren't taxonomic ranks but cirumscriptions because on the one hand they are necessary for the
concatenation of the fullname and on the other hand they are necessary for distinguishing the aggregate or species group from the microspecies." Compare subspecific aggregate for a
group of subspecies within a species!