Phylogenetic relationships of the Phocidae and population genetics of ice breeding seals

Due to their evolutionary origins among the terrestrial carnivores, the distribution of all pinnipeds (seals, sea lions, and walrus) is essentially costal or associated with ice in high latitudes. Although pinnipeds forage at sea and can maintain a pelagic existence for long periods of time, they must leave the water annually for parturition. Individuals are generally solitary and only interact socially during the highly synchronized pupping and mating season. The predictability and stability of different breeding habitats may result in varying levels of site fidelity that either promote or deter the development of population structure.; Breeding areas for species that give birth on land are easily identified, allowing for direct examinations of population structure using traditional methods such as mark-recapture and telemetry. In contrast, for many ice breeding species direct observation of movement and dispersal is not feasible due to the relative inaccessibility of their habitat. Therefore, microsatellite markers were used to investigate genetic variation and population structure in four species of Antarctic and two species of Arctic ice breeding seals.; Among the Antarctic ice breeding species examined, Ross (Ommatophoca rossii), leopard (Hydrurga leptonyx), and crabeater (Lobodon carcinophagus) seals which give birth and breed in the pack ice surrounding Antarctica, were not geographically structured. However, breeding colonies of Weddell seals (Leptonychotes weddellii ) sampled in the in the land-fast ice of Antarctica were moderately structured. In contrast, the Arctic pack ice breeding bearded seal ( Erignathus barbatus) was strongly structured throughout most of its circumpolar distribution, while populations of the land-fast ice breeding ringed seal (Phoca hispida) were genetically homogenous.; The contrasting pattern of population structure, in relation to breeding habitat, among Antarctic and Arctic ice breeding seals was examined in a phylogenetic context. The evolution of pagophilic behaviour in the Antarctic ice breeding seals has led to the loss of population structure in most species. However in the Arctic, the process leading to the evolution of population structure has been influenced by a cold adapted, ice breeding ancestor that was unable to move through areas of thick ice.