GENETIC-VARIATION OF SOUTHERN-HEMISPHERE FUR SEALS (ARCTOCEPHALUS SPP) - INVESTIGATION OF POPULATION-STRUCTURE AND SPECIES IDENTITY

We have examined phylogenetic and geographic patterns of variation in the mitochondrial cytochrome b gene of Southern Hemisphere fur seals ( Arctocephalus spp,), Our survey of 106 individuals from four putative species reveals three distinct patterns of variation reflecting ancien t, recent historic, and contemporary gene flow, For the combined sampl es of Subantarctic (Arctocephalus tropicalis) and Antarctic (Arctoceph alus gazella) fur seals, we find low levels of sequence diversity and reciprocal paraphyly of haplotypes (where representative haplotypes of a species are found to occur infrequently in another species and vice versa), For the Australian and Cape fur seal subspecies (Arctocephalu s pusillus doriferus and A. p. pusillus, respectively), we find low le vels of sequence diversity but significant differences in the regional distribution of haplotypes that are consistent with, but not conclusi ve of, the current subspecies definition based on nonmolecular data, F or the New Zealand fur seal (Arctocephalus forsteri), we find high lev els of average sequence diversity because of the survival of two diver gent lineages of mitochondrial haplotypes with differences approaching that found in interspecific comparisons of other mammals, The two div ergent clades are distributed sympatrically in some regions, but the o verall geographic structure of the variation is significant across the range of this species, These new molecular data are inconsistent with current taxonomic definitions of species within the Southern Hemisphe re fur seals and argue for reevaluation of these ''species'' definitio ns, For management purposes, the definition of evolutionarily signific ant units (Ryder 1986) and genetic management units (Moritz 1994) in r elation to these species may also be evaluated in light of this molecu lar genetic information.