Genetic introgression between native and introduced brown trout Salmo trutta L. populations in the Rhone River Basin

Authors

  • C. R. LARGIADER,

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    1. Department of Population Biology, Institute of Zoology, University of Berne, Baltzerstrasse 3, CH-3012 Berne, Switzerland
      Institut National de la Recherche, Agronomique, Laboratoire de Génétique des Poissons, 78352 Jouy-en-Josas, France. Tel.: + 33-1-34-65-23-91, Fax: + 33-1-34-65-23-90, E-mail: largiader@zoo.unibe.ch
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  • A. SCHOLL

    1. Department of Population Biology, Institute of Zoology, University of Berne, Baltzerstrasse 3, CH-3012 Berne, Switzerland
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  • The present study was part of Carlo R. Largiadèr's PhD project. This project encompassed a survey of the genetic differentiation among brown trout populations in Switzerland and the assessment of effects of stocking on the genetic variation in autochthonous populations. Professor Adolf Scholl is studying population biology. His particular interests cover taxonomic and systematic aspects in teleostean fish and arthropods.

Institut National de la Recherche, Agronomique, Laboratoire de Génétique des Poissons, 78352 Jouy-en-Josas, France. Tel.: + 33-1-34-65-23-91, Fax: + 33-1-34-65-23-90, E-mail: largiader@zoo.unibe.ch

Abstract

In the Doubs River (Rhone drainage) two distinct brown trout (S. trutta) phenotypes are observed. One phenotype is locally called Doubs trout and is characterized by four black stripes on the sides, similar to perch (Perca fluviatilis L.) and the other is the common phenotype of the fluviatile ecotype of brown trout, Salmo trutta f. fario. Protein data for three samples from the Doubs show that the Doubs trout belongs to the Mediterranean population group of brown trout, whereas the fario phenotype originates from stocking with hatchery strains of Atlantic basin origin. The two forms, however, do not hybridize freely. This is indicated by considerable gametic phase disequilibrium between alleles of hatchery and Doubs trout at one sampling site, and by lack of intermediate genotypes and phenotypes at another sampling site. The introgression patterns observed at the two sites suggest that differences in local habitat conditions can affect the degree of hybridization and introgression.

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