Morphological and genetic characterization of Sardinian trout Salmo cetti (Rafinesque, 1810) and their conservation implications

The morphological and genetic structure of Western Mediterranean trout Salmo cettii inhabiting basins in Sardinia was completed to assist the design of its conservation programmes. Genetic analysis of protein-coding LDH-C1 plus sequencing mitochondrial control region gene and analyses of morphological characters described 253 specimens from seven localities in two basins in Southwest Sardinia. Nuclear and mitochondrial analyses revealed all of the fish were pure-bred native S. cettii, with no introgression from allochthonous S. trutta. The novel 18 mtDNA control region haplotypes were clustered in an ‘insular’ clade, strictly related to the Adriatic haplogroup, and depicted a radial network around two ancestral haplotypes. Completion of discriminant analysis using data on body pigmentation and quantitative morphologic parameters revealed three phenotypic groups within the fish. Each population and phenotype, characterised by high values of nucleotide and haplotype diversity, were not genetically differentiated and not geographically structured according to the two hydrological basins. Geometric morphometric analysis, based on 15 landmarkers, revealed pronounced and highly significant differences in body shape morphology between populations, suggesting S. cettii is locally adapting to extreme environmental conditions and so future management plans for these populations should treat the two basins as distinct morphological unit

Genetic survey of endemic Sardinian trout (Salmo trutta macrostigma) populations from SIC Foresta Monte Arcosu Natural Reserve: implications for future conservation effort.

In recent years stocks of brown trout have declined in several water systems and the main causes may be related to deterioration in habitat quality and introduction of non-native salmonids. The release of invasive fish is affecting the natural brown trout genetic diversity, modifying the distribution of endemic populations and driving towards genetic pollution events. In this study, promoted and financed by the Provincia di Cagliari, we present the genetic survey of autochthonous Sardinian brown trout (Salmo trutta macrostigma) within a pilot project entitled “Recovery of autochthonous Sardinian brown trout (Salmo trutta macrostigma) within the management plan of SIC Foresta Monte Arcosu Natural Reserve”. Analyses of mtDNA D-loop segment and of nuclear LDH-C1* locus were performed on 245 individuals from 7 populations within two river basins. The nuclear data indicated only the presence of pure native species, not affected by allochthonous material of Atlantic origin. High levels of average pairwise distance were detected among the 53 mtDNA D-loop haplotypes, supporting the presence of two haplo-groups most likely evolved from within the Adriatic lineage of brown trout. Then, the haplotype distribution revealed high levels of genetic diversity in all the populations. The analysis of molecular variance (AMOVA) evidenced the absence of geographic genetic structure among two hydrogeographic basins, indicating only significant levels of genetic diversity within basin/population. From a conservation point of view these genetic results appear significant for two folders: i) they evidence the persistence of pure S. trutta macrostigma indicating the high value of the institution of conservation area dedicated for; and ii) they show that on a local geographic scale, high levels of genetic diversity are evolved, recommending the protection of this unique biodiversity hotspot produced by this insular ecosystem