Subspecies

Brown trout (Salmo trutta) exhibits dramatic variation across its range — sea trout (migratory), river brown trout, and lacustrine populations — traditionally given trinomials. Molecular studies have complicated the picture: some 'subspecies' are genetically more distinct than recognized species in other groups, while others show insufficient divergence to justify recognition. In conservation, subspecies recognition matters enormously: endangered subspecies may qualify for legal protection independently, even if the species as a whole is not threatened. The Atlantic salmon's multiple genetically distinct river populations function as semi-independent evolutionary units with important conservation implications.