PRIMARY RESEARCH PAPER Morphological and genetic characterization of Sardinian trout Salmo cettii Rafinesque, 1810 and their conservation implications Serena Zaccara . Stefania Trasforini . Caterina M. Antognazza . Cesare Puzzi . J. Robert Britton . Giuseppe Crosa Received: 26 January 2015 / Revised: 22 April 2015 / Accepted: 8 May 2015 / Published online: 20 May 2015 Ó Springer International Publishing Switzerland 2015 Abstract The morphological and genetic structure of Western Mediterranean trout Salmo cettii inhabit- ing 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 quan- titative morphologic parameters revealed three phe- notypic groups within the fish. Each population and phenotype, characterised by high values of nucleotide and haplotype diversity, were not genetically differ- entiated and not geographically structured according to the two hydrological basins. Geometric morpho- metric 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 units. Keywords Salmo cettii Á Salmo trutta Á Phenotypic forms Á Genetic variability Á Geometric morphometric analysis Á Conservation Introduction Brown trout, Salmo trutta L. 1758 (Osteichthyes, Salmonidae), is an important riverine freshwater fish due to its high social, economic and recreational value (Goudie, 1982; Suarez et al., 2001). It is widely distributed across Europe and North Africa where it has a complex mosaic of phenotypic forms and eco- ethological variability, resulting in problems in iden- tification and taxonomy (Bernatchez, 1995; Kottelat & Handling editor: Christian Sturmbauer S. Zaccara (&) Á C. M. Antognazza Á G. Crosa Department of Theoretical and Applied Sciences, University of Insubria, Via H. Dunant 3, 21100 Varese, Italy e-mail: serena.zaccara@uninsubria.it S. Trasforini Á C. Puzzi G.R.A.I.A. srl Gestione e Ricerca Ambientale Ittica Acque, Via Repubblica 1, 21020 Varano Borghi, Varese, Italy J. R. Britton Department of Life and Environmental Sciences, Faculty of Science and Technology, Centre for Conservation Ecology and Environmental Science, Bournemouth University, Poole, UK 123 Hydrobiologia (2015) 760:205–223 DOI 10.1007/s10750-015-2322-1