A review of the genetic relationships of Atlantic walrus (Odobenus rosmarus rosmarus) east and west of Greenland

Studies of the genetic variation involving allozymes, mitochondrial and nuc lear DNA (microsatellites) in walruses (Odobenus rosmarus) were reviewed. I n addition, the genetic relationships of a total of 211 Atlantic walruses, O. r. rosmarus, from 5 sampling areas west and east of Greenland were studi ed using 12 nuclear DNA-micro satellite loci and restriction fragment lengt h polymorphism obtained from the ND1, ND2 and ND3/4 segments of the mitocho ndrial DNA (mtDNA). At the mtDNA level, no divergence was observed among th e three sampling areas cast of Greenland (i.e. East Greenland, Svalbard and Franz Josef Land), whereas areas west of Greenland (i.e. Northwest and Wes t Greenland) showed some differentiation. The genetic variation at the micr osatellite loci grouped the individuals into four sub-populations: Northwes t Greenland, West Greenland, East Greenland and a common Svalbard-Franz Jos ef Land sub-population. A significant correlation between genetic distance and geographic distance between the sampling areas (isolation-by-distance e ffect) was detected, especially at the mtDNA level. At a small-scale phylo- geographical level, the mtDNA data indicated that Atlantic walruses have di verged into two major groups: one northwest (i.e. in the North Water) and o ne east of Greenland (i.e. an East Greenland- Svalbard-Franz Josef Land gro up), whereas the haplotype distribution in the West Greenland sample reflec ted a mixture of both these groups. The microsatellite data supported a gen eral grouping of walruses to the west and east of Greenland.