Item – Thèses Canada

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Numéro d'OCLC
55596453
Lien(s) vers le texte intégral
Exemplaire de BAC
Exemplaire de BAC
Auteur
Lenormand, Sophie,1973-
Titre
Évolution de l'anadromie et stratégie de reproduction chez l'omble de fontaine, Salvelinus fontinalis.
Diplôme
Ph. D. -- Université Laval, 2003
Éditeur
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [2004]
Description
2 microfiches.
Notes
Includes bibliographical references.
Résumé
In some populations, natural selection favours the maintenance of several alternative phenotypes. How a diversity of reproductive tactics evolves under natural selection remains a central issue of evolutionary biology. In salmonids, two major tactics are observed: anadromy, characterized by a migration from the natal river to salt water, and freshwater residency. The expression of these tactics is plastic and depends on individuals' growth and scope of growth in fresh water. This study, based on the brook charr population of the Sainte-Marguerite River, Saguenay, Québec, aimed at a better understanding of the existence and the maintenance of alternative tactics in salmonids, and at highlighting some of the factors involved in the evolution of anadromy. Combining samplings of resident and anadromous charr, a creel census and a mark-recapture experiment, we assessed the consequences, in terms of life-history and life-time reproductive success, of expressing anadromy or freshwater residency. Migratory patterns of anadromous charr emphasized the co-evolution of migratory behaviour and life-history. The life-history of anadromous and resident charr highlighted the existence of a trade-off between growth and survival, associated with the expression of anadromy or of residency. The use of estuarine areas enhanced growth but increased risks of mortality. Freshwater residency was associated with a poor growth but a much better survival to reproduction. In fresh water, environmental factors, such as intra- and inter-specific competition, may influence growth opportunities, and hence, reproductive prospects of individuals that adopt residency. However, we observed that a relatively recent geographical isolation (35 years) can change the reaction norm of individuals to growth opportunities and lead to a reproduction in fresh water in spite of poor growth. A high heritability of migratory behaviour and/or of traits regulating energy requirements of individuals could explain the disappearance of anadromous behaviour in isolated communities. Overall, the existence of a trade-off between growth and survival in fresh water and in estuarine areas, environmental variability and frequency-dependent selection may prevent a specialization towards anadromy or residency and favour the maintenance of phenotypic plasticity with regard to migration.
ISBN
0612826929
9780612826922