Évolution des tactiques alternatives chez l'omble de fontaine. Patrons de reproduction, héritabilité et pêche sélective

Authors: Thériault, Véronique
Advisor: Dodson, Julian J.; Bernatchez, Louis
Abstract: The central objective of this thesis was to assess the genetic basis of alternative life-history tactics in brook charr, Salvelinus fontinalis. Anadromy, defined as migration to sea before returning to freshwater to spawn, and residency, the completion of the entire life-cycle in freshwater, are two tactics commonly found in sympatry in salmonids. These two life-history forms are considered here as alternative tactics within a conditional strategy and are studied according to the threshold model of quantitative genetics. First, molecular markers and parentage analysis revealed that reproduction frequently occurred between the two forms, and was mediated by the resident males. Moreover, individual reproductive success was linked to body size in females, but not in males, which suggest that smaller males make use of the alternative sneaker reproductive tactic. Second, sib-reconstruction methods coupled to an “animal model” allowed the estimation of a significant heritability for the life-history tactic (between 0.53 and 0.56) and a significant genetic correlation between body size and tactic (-0.52 and -0.61), suggesting a joint evolution of these two traits. Finally, the evolutionary consequences of sportfishery on the evolution of anadromy and residency were assessed with the use of an eco-genetic model. After a hundred years of fishing-induced selection directed toward anadromous fish, the migration reaction norms shifted, resulting in a decrease in the probability of migrating with increasing harvest rate. This change was accompanied by a higher mean age at migration. The proportion of fish adopting the anadromous tactic decreased in the population as harvest rate increased, as did the absolute number of fish found in saltwater. These changes resulted in a lower mean age and size at maturity. This thesis contributes to our understanding of the determinism of alternative phenotypes and stands out because of its realization under completely natural conditions. By highlighting the genetic basis of anadromy and residency, this work suggests that an evolutionary response is expected in face of anthropogenic or natural selective forces, and such consequences are presented through an innovative modeling approach.
Document Type: Thèse de doctorat
Issue Date: 2007
Open Access Date: 13 April 2018
Permalink: http://hdl.handle.net/20.500.11794/19708
Grantor: Université Laval
Collection:Thèses et mémoires

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