Phylogeographic inference on the native brown trout mtDNA variation in Central Italy

Università Politecnica delle Marche, Ancona, The Marches, Italy
Italian Journal of Zoology (Impact Factor: 0.79). 06/2006; 73(2):179-189. DOI: 10.1080/11250000600679751


Genetic diversity was analysed in Salmo trutta populations living in an area of central Italy by sequencing 310 bp of the 5′ end of the mtDNA control region (D‐loop) and by Restriction Fragment Length Polymorphism (RFLP) analysis of three mtDNA segments. Data show a genetic structure profoundly altered by stockings with allochthonous material of Atlantic origin. In fact, 15 of the RFLP haplotypes detected are linked to an Atlantic sequence. The remaining 9 were instead coupled with sequences representing the three major phylogenetic lineages previously identified in the Mediterranean basin (Adriatic, marmoratus, and Mediterranean), representing the native genetic diversity of brown trout in that area. The close genetic affinity observed between these latter haplotypes and those found in the Balkan peninsula by other authors seems to be in accordance with a recent, natural, history of dispersion between the two borders of the Adriatic Sea. These results appear significant from a conservation point of view as, in spite of the massive stocking with hatchery‐reared specimens, they highlight the persistence of Salmo trutta native genetic diversity in central Italy.

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    • "represented in our analyses by a sample from the San Vena - nzio Gorges , Aterno River ( Abruzzo , Italy ) . Previous genetic analy - ses of the same sample ( Gratton et al . , 2007 ) demonstrated one of the lowest levels of allochthonous introgression among central Italian Adriatic populations ( see Caputo et al . , 2004 ; Nonnis et al . , 2003 ; Splendiani et al . , 2006 ) . A large sample of the S . carpio pop - ulation from Lake Garda was obtained from professional fishing in 2003 and 2004 . A few samples of lake - dwelling trout were caught from Lake Garda , during the feeding season or from the low Sarca River ( Lake Garda ' s main inflow ) , during the spawning migration , and were assigned to S . "
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    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).
    Full-text · Article · Jul 2014 · Molecular Phylogenetics and Evolution
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    • "Populations of brown trout in eastern Sicily have been described by Rafinesque (1810) who named the local form Salmo cettii, which according to Kottelat (1997) should be considered as the appropriate specific name of the species. However, brown trout is known to be an important aquaculture species whose captive strains are cultured throughout Europe and have often been introduced in natural environments where they have introgressed autochthonous populations (Caputo et al., 2004; Madeira, Gomez-Moliner & Machordom Barbé, 2005; Splendiani et al., 2006). In this context, identification of the polymorphism at the LDH locus (Hamilton et al., 1989; McMeel, Hoey & Ferguson, 2001) – characterized by two co-dominant alleles, the LDH C1*100 considered 'ancestral' and fixed in Mediterranean and South Atlantic lineages and the LDH C1*90 considered a 'modern' allele for brown trout, fixed in the North Atlantic lineage – contributed significantly to the identification of introgressed populations of Mediterranean brown trout, given that the northern European hatchery-reared brown trout have been shown to be fixed for the LDH-C1*90 allele, which is therefore diagnostic for this strain. "
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    ABSTRACT: Genetic introgression of aquaculture stocks in local forms is well documented in many fish species but their evolutionary consequences for the local populations have not been thoroughly explored. Due to its wide geographical range, the existence of many locally adapted forms and the frequent occurrence of introgression of aquaculture stocks in local forms, brown trout represents the ideal system to study the effects of such introgressions. Here, we focus on a group of rivers and streams in Sicily (Italy), and, by using molecular tools, we show that autochthonous populations are probably derived from the Southern Atlantic clade, which is present in the Iberian peninsula and North Africa. Three out of the four studied rivers reveal signs of genetic introgression of domestic stocks. Finally, by using advanced geometric morphometric analyses, we show that genetic introgression produces a higher degree of morphological variability relative to that observed in non-introgressed populations. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, ●●, ●●–●●.
    Full-text · Article · Jun 2014 · Biological Journal of the Linnean Society
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    • "Fra le specie considerate a rischio critico di estinzione bisogna annoverare la trota fario di ceppo mediterraneo , presente in Appennino con alcune popolazioni residue che popolano soprattutto i corsi d'acqua sui substrati geologici calcarei (Splendiani et al., 2013), altamente permeabili e in grado di attivare una ricca e costante circolazione idrica sotterranea. I salmonidi mostrano in Italia un elevato grado di differenziazione genetica (Caputo et al., 2004; Splendiani et al., 2006) e le caratteristiche di molte popolazioni, soprattutto della parte meridionale della penisola, sono ancora poco studiate (Zanetti, 2013). Tali popolazioni, già minacciate dall'introgressione con trote di ceppo atlantico utilizzate nei ripopolamenti, risultano a rischio anche a causa dell'elevata frammentazione che le caratterizza (Splendiani et al., 2013): la ridotta possibilità di scambio degli individui fra i vari demi tramite immigrazione ed emigrazione, aumenta infatti le probabilità di estinzione locale. "
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    ABSTRACT: The fish fauna of the Apennine streams related to changes in the regime of wet depositions Some researches state that climate changes could represent the main threat to biodiversity even in lotic ecosystems in the next years. Apennine streams are particularly important for conservation of fish biodiversity in Italy due to the presence of a very large number of endemic species having very limited and fragmented range of distribution. The importance of Apennine streams for the conservation purpose, can be deduced from the species included in the categories most at risk of extinction for the Italian Red List of Vertebrates reaching the rate of 54% in Umbria and 51% in the Marche. The biological implications of climate changes, as well as physiological modifications, include the moving upstream of heat-habitat for many species and the reduction of physical habitat caused by the reduction of summer water flow: presumably climate changes will worsen the environmental restrictions above all in species living on the edge of their range, in fragmented populations and restricted to limited shelters. Other factors of human impact, such as unsustainably water withdrawals, the presence of exotic species, worsening of water quality, fragmentation of river continuity can also induce negative effects on fish fauna, which overlap with climate change and making the future outcomes particularly uncertain. KEY WORDS: Apennine / fish fauna / introduction of exotic species / Minimum Vital Flow
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