title: Restricted gene flow at the micro- and macro-geographical scale in marble trout based on mtDNA and microsatellite polymorphism.
abstract: BACKGROUND
  The genetic structure of the marble trout Salmo trutta marmoratus, an endemic salmonid of northern Italy and the Balkan peninsula, was explored at the macro- and micro-scale level using a combination of mitochondrial DNA (mtDNA) and microsatellite data.
  
  
  RESULTS
  Sequence variation in the mitochondrial control region showed the presence of nonindigenous haplotypes indicative of introgression from brown trout into marble trout. This was confirmed using microsatellite markers, which showed a higher introgression at nuclear level. Microsatellite loci revealed a strong genetic differentiation across the geographical range of marble trout, which suggests restricted gene flow both at the micro-geographic (within rivers) and macro-geographic (among river systems) scale. A pattern of Isolation-by-Distance was found, in which genetic samples were correlated with hydrographic distances. A general West-to-East partition of the microsatellite polymorphism was observed, which was supported by the geographic distribution of mitochondrial haplotypes.
  
  
  CONCLUSIONS
  While introgression at both mitochondrial and nuclear level is unlikely to result from natural migration and might be the consequence of current restocking practices, the pattern of genetic substructuring found at microsatellites has been likely shaped by historical colonization patterns determined by the geological evolution of the hydrographic networks.
authors.affiliation: Dipartimento di Biologia, Università di Padova, 35121 Padova PD, Italy.
authors.forename: José M
authors.initials: JM
authors.lastname: Pujolar
authors.affiliation: Dipartimento di Produzioni Animali, Epidemiologia ed Ecologia, Università di Turin, 10095 Grugliasco TO, Italy.
authors.forename: Alvise N
authors.initials: AN
authors.lastname: Lucarda
authors.affiliation: Dipartimento di Agronomia Ambientale e Produzioni Vegetali, Agripolis, Università di Padova, 35020 Legnaro PD, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Simonato
authors.affiliation: Dipartimento di Sanità Pubblica, Patologia Comparata ed Igiene Veterinaria, Agripolis, Università di Padova, 35020 Legnaro PD, Italy.
authors.forename: Tomaso
authors.initials: T
authors.lastname: Patarnello