This thesis investigates how changes in population size and spatial movements of individuals have shaped the distribution and abundance of neutral genetic variation in the arctic fox. This is done through mitochondrial and microsatellite DNA analyses on samples covering most of the species’ distribution, but with special emphasis on Scandinavia. On the species level, nucleotide diversity was relatively low, which indicated a historical expansion in population size in connection with the onset of the last Ice Age. It is thus possible that the glacial cycles have affected the arctic fox, and other cold-adapted species, in a way opposite to their effect on temperate species. Gene flow seemed to be high among arctic fox populations on a circumpolar scale, especially between populations where lemmings are the main food source, which could be explained by the spatial synchrony in lemming fluctuations. In Scandinavia, the arctic fox went through a severe demographic bottleneck in the beginning of the 20th century. Although some genetic variation was lost during this bottleneck, the loss was much smaller than expected, probably due to post-bottleneck gene flow from Russia. The arctic fox in Scandinavia is divided into four relatively isolated populations. Within each population, dispersal seemed to be high despite the high availability of empty territories close to natal dens, which supported the hypothesis that lemming fluctuations influence arctic fox dispersal. Genetic analyses on samples collected between 1989 and 2004 indicated an ongoing genetic drift and inbreeding within the Scandinavian populations. Furthermore, individual genetic variation was negatively associated with fitness, which could be attributed to an ongoing inbreeding depression. Analyses on faecal samples suggested that arctic foxes move higher up in the mountains and farther from the tree-line during summer compared to winter. This seasonal shift in distribution is probably caused by interspecific competition from the red fox, which is likely to be higher during summer due to red fox predation on arctic fox cubs. The results presented in this thesis have several implications for the conservation of the Scandinavian arctic fox. The finding of four isolated populations within Scandinavia and an ongoing inbreeding depression suggests that the risk of extinction is higher than previously thought. Conservation actions need to be taken in all populations to be effective, and could include genetic restoration through translocation.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

In this paper we view learning as an unconstrained non-linear minimization problem in which the objective function is defined by the negative log-likelihood function and the search space by the parameter space of an origin constrained product unit neural spatial interaction model. We consider Alopex based global search, as opposed to local search based upon backpropagation of gradient descents, each in combination with the bootstrapping pairs approach to solve the maximum likelihood learning problem. Interregional telecommunication traffic flow data from Austria are used as test bed for comparing the performance of the two learning procedures. The study illustrates the superiority of Alopex based global search, measured in terms of Kullback and Leibler's information criterion.