mtDNA Genome Phylogeny of Phocid Seals

    Early molecular systematic studies of "true" Phocid seals based upon relatively short DNA sequences were able to resolve relationships among Atlantic Harbour, Ringed, and Grey Seals (Phoca, Pusa, & Halichoerus), as well as Harp and Bearded Seals (Pagophilus & Erignathus). Relationships with Pacific Hooded and Spotted seals (Cystophora, & Histriophoca) were uncertain. Analysis of complete protein-coding mitochondrial genome sequences resolves three of four branch points in 100% of bootstrap replicates. The phylogeny suggested by these data will require reconsideration of nomenclature, and previous evolutionary interpretations of behavioural, biogeographic, and cytogenetic evolution.

    The study demonstrates the behaviour of statistical (bootstrap) support with increasing amounts of sequence data. At least 4000 bp are necessary to obtain >95% confidence on the deeper branches. On the most recent branch, Pusa and Halichoerus are joined as sister species with bootstrap confidences of 48%, 60%, 67%, 78%, & 81% with re-sampling of 1, 2, 4, 8, & 13 kbp, respectively.