title: The evolutionary jigsaw puzzle of the surviving trout (Salmo trutta L. complex) diversity in the Italian region. A multilocus Bayesian approach.
abstract: Mediterranean trout populations display a diversity of phenotypes, representing a valuable model for the study of adaptation and a puzzling dilemma for taxonomists and biogeographers, which is further entangled by the widespread introgression of allochthonous genes. In this paper we analysed DNA polymorphism at multiple loci (sequence variation of the mitochondrial control region and eight nuclear fragments and length variation at eleven nuclear microsatellite loci) in representative samples of the autochthonous taxonomic diversity described in Italian trout populations (Salmo marmoratus, S. carpio, S. cenerinus, S. cettii and S. fibreni) and in samples from hatchery-originated strains of Atlantic S. trutta. We employed model-based clustering and Approximate Bayesian Computation in order to: (i) describe the phylogeographic structure of Italian autochthonous trout populations; (ii) evaluate a set of evolutionary/biogeographic models. The inclusion of hatchery-originated strains allowed to account for man-mediated allochthonous introgression in Italian populations. Our results (i) showed that the analysed sample consists of two main autochthonous evolutionary lineages, including the marble trout populations on one side ('marble' lineage) and the three peninsular populations of S. cettii, S. cenerinus and S. fibreni on the other side ('peninsular' lineage); (ii) indicated that S. carpio originated from a 'peninsular' population, with a possible, limited contribution from the 'marble' lineage; (iii) pointed out that the 'marble' lineage started diverging before the separation of the 'peninsular' lineage from Atlantic S. trutta; (iv) suggested that a model of divergence involving gene flow from the 'peninsular' population into the ancestral gene pool of 'marble' trout is most consistent with the genetic data; (v) provided evidence that the autochthonous trout gene pools in the Tyrrhenian and Adriatic basins of the Italian peninsula started diverging very recently (most likely after the last glacial maximum).
authors.affiliation: Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, I-38010 S. Michele all'Adige, Italy; Department of Biology, University of Rome "Tor Vergata", Via della Ricerca Scientifica, I-00133 Roma, Italy. Electronic address: paolo.gratton@uniroma2.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Gratton
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Via della Ricerca Scientifica, I-00133 Roma, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Allegrucci
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Via della Ricerca Scientifica, I-00133 Roma, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Sbordoni
authors.affiliation: Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, I-38010 S. Michele all'Adige, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gandolfi
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D016000:Cluster Analysis; D004272:DNA, Mitochondrial / Q000235:genetics; D051456:Gene Flow; D005828:Genetics, Population; D007558:Italy; D018895:Microsatellite Repeats; D008957:Models, Genetic; D010802:Phylogeny; D058974:Phylogeography; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D014337:Trout / Q000145:classification* / Q000235:genetics
chemical_list: D004272:DNA, Mitochondrial
keywords: Approximate Bayesian Computation; Microsatellite; MtDNA; Nuclear DNA sequences; Phylogeography; Salmo