Conservation Genetics of Mediterranean Brown Trout in Central Italy (Latium): A Multi-Marker Approach

Abstract

Brown trout is considered a complex of incipient species, including several phylogenetic lineages, whose natural distribution in the Mediterranean area has been altered, since the beginning of the 1900s, by massive introductions of domestic strains of Atlantic origin to support fisheries. Introduced trout naturalize in new suitable environments and extensively hybridize with native populations. Here, we characterized putatively neutral and adaptive genetic variability and population structure of Mediterranean brown trout from six river catchments in central peninsular Italy, as revealed by both mitochondrial (Control Region) and nuclear (microsatellites, LDH-C1, major histocompatibility complex) markers. We quantified the admixture of wild populations with hatchery strains and evaluated the effects of domestic trout introductions on shaping population genetics. Our analyses indicated: (1) a composite picture of genetic variability in the area, with the presence of all native Mediterranean trout mitochondrial lineages (“Adriatic”, “Mediterranean”, “marmoratus”), various frequencies of allochthonous genotypes and different rates of introgression among sampling sites; (2) asymmetric mito-nuclear introgression; (3) increasing nuclear marker diversity with increasing levels of admixture across populations; (4) strong population structure coupled with relatively low effective population size. Data allowed the identification of five management units and we propose specific actions to support ongoing and future conservation strategies within the examined area.

Phylogeography of Sarmarutilus rubilio (Cypriniformes: Leuciscidae): Complex Genetic Structure, Clues to a New Cryptic Species and Further Insights into Roaches Phylogeny

“…Indeed, these mountains, despite isolating the Tyrrhenian and Adriatic slopes of Central Italy and being considered the natural border between TL and PV districts and between TL and the northern Adriatic section of AC, could have acted as a semi-permeable barrier. This seems plausible especially for rheophilic species [ 101 ], through river connections acting in the upper section of basins [ 102 ], and as already reported in Mediterranean trout [ 103 , 104 ]. Sarmarutilus rubilio is not a strict rheophilic species; however, it is found in Apennine rivers and could have spread through the hydrographic network, which could explain the presence of HpA01 in the Adriatic slope (TRO and FOR) and the high differentiation observed in those sites that are not linked to the Apennines, i.e., ARR drainage that is fed by the Bracciano volcanic lake [ 105 ].…”

“…Alternatively and in addition, a human-driven translocation of lineage A in the Magra-Vara basin could not be excluded, but it is unlikely as all allochthonous species present in this basin are those typical of the northern PV district [ 99 ], suggesting the translocation of fishes only from geographic areas where S. rubilio is absent. Mitochondrial lineage A, besides being the most widespread, is also the most frequent when coexisting with the others ( Figure S3 ); therefore, we cannot exclude a higher fitness associated with lineage A and/or some kind of competition when secondary contact occurs, as suggested in other freshwater fishes when different lineages come in contact [ 104 ].…”

The role of semen cryobanks for protecting endangered native salmonids: Advantages and perspectives as outlined by the LIFE Nat.Sal.Mo. project on Mediterranean brown trout (Molise region – Italy)

“…it, accessed on: 28 July 2022). This situation has prompted the development of many conservation projects aiming at restoring the genetic integrity of Mediterranean trout populations in Italy (Sabatini et al, 2018;Lorenzoni et al, 2019;Splendiani et al, 2019;Rossi et al, 2022), including Molise region (Rusco et al, 2019;Rusco et al, 2020), where, in 2018 the "LIFE" Nat.Sal.Mo project was born.…”

Identification of Ancestry Informative Markers in Mediterranean Trout Populations of Molise (Italy): A Multi-Methodological Approach with Machine Learning

“…Among the others, brown trout ( S. trutta ) has traditionally attracted the attention of conservation biologists and public institutions due to its iconic significance for fishery management and aquaculture. Brown trout is considered a complex of incipient species [ 3 , 4 ], which counts several phylogenetic lineages including Mediterranean trout [ 5 ]. Recently, many conservation projects have been proposed to restore the genetic integrity status of Mediterranean trout populations in Italy [ 5 , 6 , 7 , 8 , 9 , 10 ], mainly threated by introgressive hybridization between native and commercial hatchery strains, often introduced for meeting fishing demands and for recreation activities.…”

“…Brown trout is considered a complex of incipient species [ 3 , 4 ], which counts several phylogenetic lineages including Mediterranean trout [ 5 ]. Recently, many conservation projects have been proposed to restore the genetic integrity status of Mediterranean trout populations in Italy [ 5 , 6 , 7 , 8 , 9 , 10 ], mainly threated by introgressive hybridization between native and commercial hatchery strains, often introduced for meeting fishing demands and for recreation activities. Morphological features (such as number of parr marks, adipose fin color pattern and number of black opercular spots [ 11 ]) have been successfully adopted in order to quickly differentiate among native, farm-reared and hybrid specimens during preliminary steps of monitoring activities [ 11 ] but the use of genetic markers remains pivotal to conduct a truly effective restoration project [ 12 ].…”