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Variation is slight across this species' Holarctic range, probably because of its nomadic habits and dispersal over broad areas (see Demography and Populations). Population genetic analysis revealed no phylogeographic structure from three distinct geographic regions-Scandinavia, e. Siberia, and n. North America-and high levels of gene flow in the recent past and, perhaps, currently (Marthinson et al. 2008).
No subspecies recognized, although note that Bubo scandiacus (Linnaeus, 1758) has many junior synonyms: Strix nyctea Linnaeus, 1758; B. s. arcticus (Bartram, 1792); B. albus Daudin, 1800; B. s. nivea (Thunberg, 1798); S. candida Latham, 1802; S. erminea Shaw, 1809; B. s. europea (Brehm, 1866); and B. s. americana (Brehm, 1866).
As a group, the owls (Strigiformes) were long considered to be related most closely to the nightjars (Caprimulgiformes), yet cladistic (e.g., Cracraft 1981) and molecular (e.g., Wink and Heidrich 1999) data have suggested that these groups are not related. A recent multigene phylogeny of birds (Hackett et al. 2008) supported this alternative: it placed the Strigiformes sister to the Coliiformes (mousebirds) and argued for a shared history between Strigiformes + Coliiformes and such avian orders as Trogoniformes (trogons), Coraciiformes (rollers, kingfishers, and allies), and Piciformes (woodpeckers, toucans, and allies).
Within Strigiformes, a long-posited deep division between the barn and bay owls (Tytonidae) and all other ("typical") owls (Strigidae) has been upheld by all molecular work, and within the Strigidae, the large eared owls are part of a clade that also includes Strix, Ciccaba, and (probably) Pulsatrix wood owls (Wink and Heidrich 1999, 2000).
The nearest relative of B. scandiacus is unclear, but molecular data suggest that B. virginianus, the Great Horned Owl of the Americas, may be its evolutionary sister (Mindell et al. 1997, Wink et al. 2009). The two species are estimated to have diverged ~4 mya (Wink et al. 2009). They are broadly similar in voice and hooting posture and have a similar number and structure of chromosomes, and macro-autosomes (Belterman and de Boer 1984); yet differences in plumage and skeleton (Ford 1967) have led some to retain B. scandiacus in the monotypic genus Nyctea (e.g., Weick 2006, Potapov and Sale 2012). Recent interbreeding, in captivity, of a male B. scandiacus with a female B. bubo, the Eurasian Eagle Owl (H. Mikkola, pers. comm.), underscores the close evolutionary relationship with the large eared owls.