Comments: Patterns of geographic variation in skull morphology showed that although ringed seals from Lake Ladoga and Saimaawere considerably differentiated, specimens from other localities were not distinguishable from each other, suggesting similar selection pressure or extensive gene flow especially in the Arctic basin (Amano et al. 2002). These authors considered it reasonable to recognize 5 subspecies in P. hispida: P.h. hispida, P. h. botnica, P. h. ladogensis, P. h. ochotensis, and P. h. saimensis.
The ringed seal was placed in the genus Pusa by Muizon (1982), Rice (1998), Baker et al. (2003), Wozencraft (in Wilson and Reeder 2005), and some other authors, but regarded (with the nominal genera Histriophoca and Pagophilus) as a member of the genus Phoca in other literature (e.g., King 1983; Riedman 1990; Nowak 1991; Reeves et al. 1992; Wozencraft, in Wilson and Reeder 1993).
A cladistic analysis of mtDNA data yielded three clades among northern seals: Phoca-Pusa-Halichoerus, Cystophora-Pagophilus, and Erignathus (Perry et al. 1995). Each clade may be regarded as a tribe of the subfamily Phocinae. The magnitude of the differences among Phoca, Pusa, and Halichoerus was on the same order as that between species and subspecies within the genus Odocoileus. Because Cystophora is the closest relative of Pagophilus, the latter cannot be regarded as congeneric with Phoca; the differences between the two are great enough to justify placing them in separate genera (Perry et al. 1995).
Mouchaty et al. (1995) examined the cytochrome b gene and found a close phylogenetic relationship between Pusa hispida and Halichoerus grypus, which, they noted, merits further study.
Árnason et al. (1995, 2006) assigned Pusa, Phoca, and Halichoerus to subgenera within Phoca. Noting the morphological distinctness of Halichoerus, Fulton and Strobeck (2010) considered the generic distinctions to be unresolved. NMFS follows Burns and Fay (1970) and Árnason et al. (2006) and classify ringed seals as Phoca hispida with the recognition that molecular and morphological analyses remain incompletely resolved (Kelly et al. 2010).
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