Dynamique de l'organisation géographique de la diversité génétique chez l'omble de fontaine Salvelinus fontinalis Mitchill : diversité des habitats et des histoires de vie

Authors: Castric, Vincent.
Advisor: Bernatchez, Louis
Abstract: The expected concordance between landscape structure and geographic patterns of genetic structure is due to landscape constraints over potential coalescence among alleles. In the long run, a high level of concordance may thus be expected. Why then is concordance sometimes so weak? First, species have a history, such that landscape disturbances can affect geographic patterns of diversity. Second, species are seldom “ideal”, as defined by population genetic models, such that their demographic properties can vary in space and in time. For instance, migration rates can vary within the species’ range because the form of dispersal can evolve. Brook charr populations in coastal areas is an especially useful model system to empirically investigate the consequences of simple departures from population genetic models because landscape constraints can generally be easily identified, because recent disturbances of north-eastern North America have been extensively described, and because the dynamic of anadromy, brook charr’s form of dispersal in coastal areas, has been ecologically characterized in the frame of seasonal migrations between freshwater and saltwater. Although lakes and rivers strongly constraint migration pathways, geographic patterns of diversity in lacustrine populations were only weakly correlated with landscape structure, especially at large geographic scales. Temporal variation of isolation by distance along a colonization gradient then revealed that spatial patterns of genetic diversity were still evolving toward stable equilibrium. The species’ form of dispersal was also evolving along this gradient, according to variation of the inbreeding load. Our results thus revealed some aspects of the dynamics of genetic diversity in natural populations. Understanding its evolution requires that biogeographic considerations be included into the view of genetic variation in space. Because the accuracy of demographic inference methods would be impaired by spatial and temporal variations in habitat constraints, a strictly comparative approach is proposed as an alternative in empirical population genetics studies.
Document Type: Thèse de doctorat
Issue Date: 2002
Open Access Date: 11 April 2018
Permalink: http://hdl.handle.net/20.500.11794/17786
Grantor: Université Laval
Collection:Thèses et mémoires

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