Geographic distribution of mitochondrial cytochrome b DNA haplotypes in New Zealand fur seals (Arctocephalus forsteri)

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Abstract
Nucleotides spanning 361 base pairs of the 5′ portion of the mitochondrial cytochrome b gene were sequenced from 16 New Zealand fur seals, Arctocephalus forsteri, representing seven rookeries in three different regions: the east and west coasts of New Zealand, and Western Australia. Five different mitochondrial haplotypes were observed in these novel sequence data for this species. The geographical distribution of the cytochrome b haplotypes was shown to be heterogeneous by three statistical tests. The major finding of this study is the difference between haplotypes found in fur seals from Western Australian rookeries and haplotypes found in fur seals from New Zealand rookeries. The nucleotide sequence difference found in pairwise comparisons among the surveyed individuals is in the range 0.3–0.8%. One individual showed an unexpectedly large sequence divergence (range 3.3–4.2%) from all other fur seals in this study. We compare alternative hypotheses that this individual is a descendant of an ancient maternal lineage which survived a population bottleneck, that New Zealand fur seals exhibit a rather large amount of genetic variability at this locus, or that this particular individual is a hybrid. Western Australian rookeries were extirpated as a result of sealing during the early 1800s. The geographic distribution of mitochondrial cytochrome b haplotypes suggests that the extirpated Australian rookeries were not recolonized by migrants from New Zealand. No genetic division between fur seal populations sampled from the east and west coasts of New Zealand is revealed using this region of the mitochondrial genome as a genetic marker, but we suggest that it should be possible to create a more discriminating test by examining a more variable DNA target such as the mitochondrial control region.

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