Danubian Lineage Research Articles

Unravelling the identity of lake ecotype of brown trout (Salmo trutta) in Slovenia: genetic insights and conservation implications

Abstract The genetic identity and conservation status of lake ecotype of brown trout (Salmo trutta) populations in Slovenia’s Alpine lakes Bled and Bohinj have been subjected to changes due to historical stocking practices. We aimed to evaluate the genetic differentiation and origins of these populations to advise for correct conservation strategies. Using microsatellite and mitochondrial DNA analysis on 365 trout specimens, we explored the genetic diversity and structure of these populations, comparing them with potential originators. Results revealed distinct genetic profiles between Bled and Bohinj lake trout, with Bohinj lake trout closely aligned with the native Danubian lineage and Bled lake trout showing a hybrid composition, significantly influenced by hatchery-introduced Atlantic lineage strains. The genetic distinction between these populations underscores the complexity of their conservation, showcasing the impact of human-mediated introductions on natural populations. The urgent need for conservation measures to preserve the Bohinj population’s native genetic pool is highlighted, underlining the must to prevent the transfer of individuals from Lake Bled or elsewhere and to reconsider stocking practises in order to prevent further genetic dilution of these iconic European lake dwellers.

Application of the geometric morphometrics approach in the discrimination of morphological traits between brown trout lineages in the Danube Basin of Croatia

Brown trout is a salmonid fish with a natural range extending throughout western Eurasia and North Africa. Due to its commercial value, it has also been introduced worldwide. In continental Croatia, introduced trout of the Atlantic lineage hybridizes with native trout of the Danubian lineage, threatening the native genetic diversity. The geometric morphometrics approach was used in this study to analyse changes in shape between native trout, introduced trout and their hybrids, classifieda prioriby molecular phylogenetic analyses. A total of 19 landmarks and semi-landmarks were used to capture the shape of 92 trout individuals belonging to two lineages and their hybrids. Canonical variate analysis and discriminant function analysis were used to analyse and describe shape variation. A significant difference was found between the shape of the Atlantic lineage trout and both Danubian lineage trout and hybrids, with the most prominent differences in body depth, head length and eye size. No statistically significant shape differences were observed between Danubian lineage trout and the hybrids. The observed significant differences in shape could be the result of genetic diversity or trout phenotypic plasticity. Further studies are needed to clarify the origin of this variation in shape.

Alternative Life-History in Native Trout (Salmo spp.) Suppresses the Invasive Effect of Alien Trout Strains Introduced Into Streams in the Western Part of the Balkans

Diversity of native trout fish Salmo spp. comprises a variety of nominal taxa in Serbia, Montenegro and Bosnia and Herzegovina. Recent mapping of the resident trout detected brown trout S. trutta (sensu stricto) of the Atlantic (AT) mtDNA lineage introduced into populations of both tentative Danubian trout S. labrax and of tentative Adriatic trout S. farioides belonging to the Danubian (DA) and Adriatic (AD) mtDNA lineages, respectively. In addition, an introduction of the tentative Macedonian trout S. macedonicus of the AD lineage was detected in the one native population of the tentative S. labrax. In almost all recipient non-migratory trout populations, a cross breeding between the native and introduced trout was detected by heterozygosity in either only LDH-C nuclear locus, or in LDH-C and particular microsatellites’ loci. Exception is one population where both resident and migratory, lake-dwelling individuals of the tentative Adriatic trout spawned at the downstream section of a stream in Montenegro, none of microsatellites’ alleles of Atlantic brown trout that were introduced into the upstream section was detected. The occurrence of cross breeding between Adriatic and brown trout was evident in the upstream, isolated section. It seems that migrating, lake-dwelling Adriatic trout in combination with their resident, stream-dwelling conspecifics suppress introgression of genes from those situated upstream, strongly introgressed by brown trout. Having this in sight, it is noteworthy to warn on the occurrence of the migratory brown trout in the Danube River at the broader Iron Gate Gorge area. They were recorded to migrate in late summer and early fall from the Iron Gate One reservoir to the lower sections of tributaries devoid of any trout fish. However, some of those streams home very special native trout of the DA lineage in their short-extending upper sections. Those native trout populations are so far still out of contact with the reservoir-dwelling trout. However, having in mind the resilience of trout featuring the migratory life-history, the outcome of this introduction could be deleterious for those natives very precious in conservational sense.

Experimental crossbreeding reveals variation in growth among brown trout (Salmo trutta) strains and their reciprocal crossbreeds

The purpose of the current study was to evaluate culturing potential of Brown trout (Salmo trutta) strains belonging to Danubian lineage and their reciprocal crosses. Using all possible combinations F1 generation cross-types were produced by crossing Abant (A), Black Sea (L), Caspian (C) and Anatolian (F) strains of brown trout which were previously recognized as different species. Growth performance and growth parameter indices of fourteen out of sixteen cross-types were evaluated. Growth performances of nine of the cross-types were monitored for eighteen months in trial-I, rest of them (5 cross-types) were monitored for ten months in trial-II. The mean weight of fish reached 455.4 ± 7.27 g (LL) and 87.36 ± 12.03 g (AF) in first and second trials, respectively. The mean weights of the cross-types were similar at the end of the 18-months in trial-I and no significant difference was observed between cross-types except for CC and CL. The highest growth rate was observed in LL, LA and LC cross-types at the end of the 18-month. The mean weights of the cross-types were similar at the end of the 10-month period in trial-II and no significant difference was observed between cross-types except for FF and FL. The highest growth rate was observed in LL, AF and FA cross-types at the end of the 10-month. The best FCR were calculated for LL, LA, LC and AL cross-types in trial-I and LL, AF and FA cross-types in trial-II. Direction of the crossbreeding and maternal effect appeared to be decisive on growth performance of the cross-types. Along with selective breeding for better growth traits Black-Sea strain (LL), LA, LC and AF cross-types have a promising potential for aquaculture.

Genetic and molecular evidence that brown trout Salmo trutta belonging to the Danubian lineage are a single biological species.

We tested for reproductive isolation between Salmo trutta abanticus, S.t. labrax, S.t. caspius and S.t. fario by conducting crosses to produce F1 and F2 offspring. We also estimated the extent of genetic divergence between all three entities by examining sequence variation across the coI, d-loop and cytb mitochondrial genes. All of the F1 cross-types were successfully produced. After 2 years of culturing, F2 generation were produced as well. Fertilization, hatching and survival rates and hatching performance of F1 and F2 generations were evaluated. F2 generation had similar performance to their parent. Fertilization, hatching, larval survival rate and hatchery performance of F1 and F2 generation were similar except pure bred F2 S.t. abanticus. Purebred F1 individuals shared similar coloration patterns and spots with their parents but direction of the hybridization appeared to be decisive on morphology of hybrids. Some of the hybrids exhibit different morphological characters than their parents. Based on partial alignments of the three genes, phylogenetic analysis showed that these S. trutta are gathering within the same clade and appeared as monophyletic group. We found that there were some morphologic and genetic variation among S. trutta subspecies but the degree of variation does not warrant species level recognition. These findings indicate that the four subspecies constitute a single biological entity, corresponding to different morphs of the Danubian lineage. We therefore recommend that S. trutta belonging to Danubian lineage in Turkey be referred to as Salmo trutta and that strains be named according to location, such as Abant, Caspian, Black Sea and Anatolian.

The genetic status of the Hungarian brown trout populations: exploration of a blind spot on the European map of Salmo trutta studies.

BackgroundAnalyses of the control region sequences of European brown trout populations’ mitrochondrial DNA have revealed five main evolutionary lineages (Atlantic, Danubian, Mediterranean, Adriatic, Marble) mostly relating to the main water basins; however, the hybridization between lineages were increasingly reported. Due to the hydrogeography of Hungary, wild populations should theoretically belong to the Danubian lineage, however, this has not been verified by genetic studies.MethodsIn our study multiple molecular marker sets (mitochondrial sequence, microsatellites, PCR-RFLP of nuclear markers and sex marker) were used to investigate the genetic composition and population genetics of the brown trout populations in two broodstocks, six wild streams in Hungary and one Serbian population.ResultsThe admixture of Atlantic and Danubian lineages in these populations, except the Serbian population with pure Danubian origin, was observed by control region sequences of mitochondrial DNA and PCR-RFLP markers in the nuclear genome, and one unpublished Danubian haplotype was found in Hungarian populations. A sex-specific marker revealed equal gender ratio in broodstocks and Kemence stream, whereas in other wild streams the proportion of female individuals were less than 50%. Structure and principal component analyses based on the alleles of microsatellite loci also revealed overlapping populations, however the populations were still significantly different from each other and were mostly in Hardy-Weinberg equilibrium.DiscussionStocking and migration can have a significant genetic impact on trout populations of wild streams, however there are no guidelines or common practices for stocking of small streams in Hungary, thus the genetic background of these populations should be considered when developing conservation actions.

Diversity of brown trout Salmo cf. trutta in the River Danube basin of Western Balkans as assessed from the structure of their mitochondrial Control Region haplotypes

The part of the River Danube basin in the Western Balkans region (11 sampled localities and 57 in total with using of published data) revealed the remarkable diversity of brown trout assessed using the Control Region (CR) of mitochondrial DNA (mtDNA) as a molecular marker. The greatest number of brown trout populations holds brown trout of the Da1 haplotype. Particular distinct haplotypes are limited to isolated brown trout stocks. There are haplotypes of Danubian (Da), and those of Atlantic (At), Adriatic (Ad) and marmoratus (MA) lineages introduced there. Phylogenetic relationships inferred between them implicate the plesiomorhic character of Da*Vr, Da*Dž and Da-s6 haplotypes that were resolved as ancestral clades, with the intermediate position between clades holding haplotypes of the non-Danubian lineage and more advanced haplotypes of the Danubian lineage. A uniform rate of evolution was found for all clades. The recent widespread distribution and exclusivity of Da1 haplotype imply its ancestral character among advanced Danubian haplotypes. Populations in the Sava, Drava, Una and Drina revealed an expansion, whereas those in the Kupa and Zapadna Morava catchments revealed both stability in size and great differentiation. Gene flow between stocks was found to be negligible.

Thermal sensitivity of white muscle lactate dehydrogenase isolated from a lake trout, (Salmo trutta), inhabiting lake Plav, Montenegro

To shed light on thermoadaptive properties of Salmo trutta from lake Plav (Montenegro), we undertook kinetic studies of pyruvate reduction rates and thermal stability analyses of white muscle LDH. We compared these with the data obtained for trout of the same, confirmed by us, Danubian lineage living in rivers and streams of Serbia and Montenegro. We also tested the effect of acclimation in captivity at 4 and 14 °C. The lake trout was of a typical smoltified phenotype (the size, the elongated silver colored body). At physiological substrate concentration, the breaks in the Arrhenius plots (critical temperature - Tc) correlated with acclimation temperatures or habitat water temperatures. Q10 values for temperatures above Tc were close to one, in all cases except 4 °C acclimated trout. At temperatures below Tc Q10 was close to two, except in the case of 14 °C acclimated trout. Lake trout had a highest Q10 values at temperatures below Tc. It was conspicuous that within the entire range of tested temperatures the differences in Q10 resulted from the effect of environmental temperature. Higher Q10 values were obtained with LDH isolated from trout acclimated to 4 °C compared with LDH acclimated to 14 °C. Ea values were much lower at a temperature below Tc compared with temperatures above Tc. Thermal stability of muscle LDH was lower after acclimation to 14 compared to 4 °C, while extremely high thermostability was obtained with the lake trout enzyme. Our data support the concept that Tc values have distinct physiological significance.

Haplotype diversity of brown trout Salmo trutta (L.) in the broader Iron Gate area

Mitochondrial DNA (mtDNA) haplotypes of brown trout (Salmo trutta L.) populations in the area of Djerdap National Park were analyzed in order to determine their phylogeographic statuses. Sequencing the control region of mtDNA in 66 specimens from 9 streams in the broader Iron Gate area revealed that 7 brown trout from those streams carried haplotypes of Atlantic lineage, while the remaining 59 fish were of Danubian lineage, either of Da23c or Da1 haplotypes. Four streams were inhabited by populations of the indigenous Da23c mtDNA haplotype, while the population in one stream had the Da1 haplotype. In the remaining 4 streams, brown trout of exclusively Atlantic lineage were present in 3, while those of the Da23c haplotype were additionally present in the fourth. The significant fixation index Fst in all populations, caused by a significantly large proportion of the among-population component of variance, revealed the fixation of particular haplotypes in the majority of populations. The size of a particular stream determines native brown trout abundance and limits their suitability for restorative purposes.

Genetic Background and Population Genetics of Hungarian Brown Trout Populations Using PCR-RFLP and Microsatellite Markers

Event Abstract Back to Event Genetic Background and Population Genetics of Hungarian Brown Trout Populations Using PCR-RFLP and Microsatellite Markers Ágnes Ősz1* 1 Szent István University, Department of Aquaculture, Hungary Ősz Á 1, Kovács B 1, Kánainé Sipos D 1, Hoitsy Gy 2, Snoj A 3, Keszte Sz 1, Sáfrány AJ 1, Herzinyák Z 1, Kaczkó D 1, Palkó Cs 4, Urbányi B 1, Horváth Á 1 1 Department of Aquaculture, Szent István University, Páter K. 1, 2100 Gödöllő, Hungary 2 Hoitsy & Rieger Kft., Erzsébet 55, 3517 Lillafüred, Hungary 3 Department of Animal Science, University of Ljubljana, Groblje 3, 1230 Domzale, Slovenia 4 University of West Hungary, Mosonmagyaróvár Vár 2., 9200 Mosonmagyaróvár, Hungary Based on the analyses of the mitochondrial DNA of several European brown trout populations, five evolutionary lineages of brown trout were indentified (Atlantic, Danubian, Mediterranean, Adriatic, Marble). The species is bred primarily for stock enhancement of natural waters, however the most hatchery-maintained broodstocks originate from the Atlantic lineage. Due to the hydrogeography of Hungary our stocks should theoretically belong to the Danubian lineage; however, this has not been investigated earlier by genetic studies. For our genetic analysis, 702 fin clips were collected from two brown trout broodstocks (Lillafüred and Szilvásvárad) as well as populations of natural streams (Bán, Jósva, Kemence, Apátkút, Bittva and Kölöntés) in Hungary. Sequencing of the control region in mitochondrial DNA, three PCR-RFLP (mitochondrial DNA control region, lactate dehydrogenase and somatolactin genes) and five microsatellite markers were used to distinguish between Danubian and Atlantic lineages of brown trout. The proportion of the mitochondrial haplotype of the Danubian lineage was low, with the exception of the Apátkúti, Kölöntés streams and Szilvásvárad broodstock. Analyses of nuclear PCR-RFLP and microsatellites markers showed various distributions of alleles characteristic of the Atlantic or Danubian lineages, although the Atlantic genotype has dominated in all population. In case of the analyses of microsatellites the polymorphism varied greatly at all locations. In addition we found several alleles that were not described earlier in other populations. Those alleles probably would be typical of Hungarian brown trout populations. Overall the populations were effectively in Hardy-Weinberg equilibrium for both PCR-RFLP and microsatellite markers. The remarkably high proportion of allochthonous Atlantic alleles in the analyzed sites is a clear indicator of the import and stocking of non-native individuals. According to these findings, further stocking of brown trout in Hungary should be conducted in more controlled conditions. Acknowledgements This work was supported by 8526-5/2014/TUDPOL and GOP-1.1.1-09/1-2010-0141 projects. Keywords: salmo trutta, PCR-RFLP, microsatellites, lineage, Mitochondrial DNA (mtDNA) Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Phylogeny, Systematics and Genetics Citation: Ősz Á (2015). Genetic Background and Population Genetics of Hungarian Brown Trout Populations Using PCR-RFLP and Microsatellite Markers. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.FMARS.2015.03.00240 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Dec 2015; Published Online: 21 Dec 2015. * Correspondence: Miss. Ágnes Ősz, Szent István University, Department of Aquaculture, Gödöllő, 2100, Hungary, sengazso@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ágnes Ősz Google Ágnes Ősz Google Scholar Ágnes Ősz PubMed Ágnes Ősz Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effects of Stocking With Brood Fish To Management With Resident Stream Dwelling Brown Trout Salmo cf. trutta L. Stock

Management with the indigenous stock of resident brown trout Salmo cf. trutta of the Danubi-an strain in the protected area of the River Gradac with the catch-and-release fishing regime since 2000 resulted in the prime fly fishing stream in Serbia. Stocking with the brown trout parr in 2007 in the density issued by fisheries management plan supplemented with the large-sized brood fish beyond the issued fisheries measures in the upper section of the River Gradac was followed by change in structure of fish community and population structure of brown trout there. The time of maturation of brown trout was delayed and their size at maturation increased in 2008, due to the abrupt decrease in the density of their stock. That change did not affect an increase of brown trout mean weight, but only an increase of their average age, with the de-crease in relative abundance, relative biomass and annual natural production, implying the pro-longed recovery period of brown trout stock in the upper section of the River Gradac. In con-trast to that, stocking with brown trout parr only in the density issued by fisheries management plan was beneficial on the second, downstream situated section. Another prominent feature that followed stocking as a management measure was the introgression of brown trout of the Atlan-tic lineage into the gene pool of brown trout of the native, Danubian lineage, as confirmed in wild-bred brown trout.

Genetic diversity and phylogenetic origin of brown trout Salmo trutta populations in eastern Balkans

The study focuses on the phylogenetic origin and genetic diversity of brown trout in the eastern part of the Balkan Peninsula. It further aims to reveal the impact of human-mediated transfers and stocking with non-indigenous trout on the populations in this area. For these purposes, mtDNA control region and microsatellite variation of 204 individuals from 16 populations were analysed. The results indicate that mtDNA haplotypes from the lower Danube basin and southern Black Sea basins differ substantially from a subclade of the Danubian lineage consisting of haplotypes found so far in the most of the Danube basin and in the Caspian and Aral Sea basins. Considering also the results of demographic analyses, this study evidences a complex evolutionary history of brown trout in the southern and western parts of the Black Sea basin. In the Aegean Sea basin, a high frequency of the central haplotype of Adriatic mtDNA lineage has been found. The other Adriatic lineage haplotypes found in this basin differ from the central haplotype by one mutational step only, indicating a recent evolution of the Adriatic lineage in the Aegean Sea basin. Substantial genetic differentiation among populations and basins was revealed. The hybridization with Atlantic brown trout was indicated in both sea basins, but especially in the Danube basin. Compared to other European regions, it can be inferred that the introgression of exogenous brown trout in the eastern Balkan populations is rather low.

Genetic variation in brown trout Salmo truttaacross the Danube, Rhine, and Elbe headwaters: a failure of the phylogeographic paradigm?

BackgroundBrown trout Salmo trutta have been described in terms of five major mtDNA lineages, four of which correspond to major ocean basins, and one, according to some authors, to a distinct taxon, marbled trout Salmo marmoratus. The Atlantic and Danubian lineages of brown trout meet in a poorly documented contact zone in Central Europe. The natural versus human mediated origin of the Atlantic lineage in the upper Danube is a question of both theoretical and practical importance with respect to conservation management. We provide a comprehensive population genetic analysis of brown trout in the region with the aim of evaluating the geographic distribution and genetic integrity of these two lineages in and around their contact zone.ResultsGenetic screening of 114 populations of brown trout across the Danube/Rhine/Elbe catchments revealed a counter-intuitive phylogeographic structure with near fixation of the Atlantic lineage in the sampled portions of the Bavarian Danube. Along the Austrian Danube, phylogeographic informative markers revealed increasing percentages of Danube-specific alleles with downstream distance. Pure Danube lineage populations were restricted to peri-alpine isolates within previously glaciated regions. Both empirical data and simulated hybrid comparisons support that trout in non-glaciated regions north and northeast of the Alps have an admixed origin largely based on natural colonization. In contrast, the presence of Atlantic basin alleles south and southeast of the Alps stems from hatchery introductions and subsequent introgression. Despite extensive stocking of the Atlantic lineage, little evidence of first generation stocked fish or F1 hybrids were found implying that admixture has been established over time.ConclusionsA purely phylogeographic paradigm fails to describe the distribution of genetic lineages of Salmo in Central Europe. The distribution pattern of the Atlantic and Danube lineages is extremely difficult to explain without invoking very strong biological mechanisms.The peri-alpine distribution of relict populations of pure Danubian lineage brown trout implies that they colonized headwater river courses post-glacially ahead of the expansion of the Atlantic lineage. The recognition of natural as opposed to anthropogenic introgression of the Atlantic lineage into Danubian gene pools is of fundamental importance to management strategies.

The effect of domestication on a brown trout (Salmo trutta m fario) broodstock in Hungary

Molecular markers (PCR–RFLP and microsatellite) were used to investigate the genetic background of the only brown trout (Salmo trutta m fario) broodstock in Hungary which due to the hydrogeography of the country should theoretically belong to the Danubian lineage. PCR–RFLP (mitochondrial DNA control region and lactate dehydrogenase and somatolactin genes) as well as microsatellite (BFRO002, OMM1064, Ssa408uos, SsoSL417, SsoSL438) markers were used to distinguish between Danubian and Atlantic lineages of brown trout in the Lillafured broodstock. Altogether 435 fish were tagged during the experimental period. Due to mortalities, fin clips were collected from 401 individuals. According to the genetic analysis of the mitochondrial DNA, the Danubian haplotype is present in only one individual (0.2 %) of the broodstock. Analysis of the nuclear markers revealed that alleles characteristic of both the Atlantic and the Danubian lineages are found in the population. However, Atlantic alleles dominate throughout the broodstock which is in Hardy–Weinberg equilibrium according to the investigated markers. Results indicate that the original broodstock that was introduced to the farm following its construction in 1933 was of the Atlantic lineage. Although later fish from a local stream were collected and added to the broodstock, the number of these was limited and they were almost exclusively males. Fish from this farm that are stocked by anglers can have a significant genetic impact on trout populations of natural streams.

Phylogeography, genetic structure, and conservation of the endangered Caspian brown trout, Salmo trutta caspius (Kessler, 1877), from Iran

The Caspian Sea, the largest inland closed water body in the world, has numerous endemic species. The Caspian brown trout (Salmo trutta caspius) is considered as endangered according to IUCN criteria. Information on phylogeography and genetic structure is crucial for appropriate management of genetic resources. In spite of the huge number of studies carried out in the Salmo trutta species complex across its distribution range, very few data are available on these issues for S. trutta within the Caspian Sea. Mitochondrial (mtDNA control region) and nuclear (major ribosomal DNA internal transcribed spacer 1, ITS-1, and ten microsatellite loci) molecular markers were used to study the phylogeography, genetic structure, and current captive breeding strategies for reinforcement of Caspian trout in North Iranian rivers. Our results confirmed the presence of Salmo trutta caspius in this region. Phylogenetic analysis demonstrated its membership to the brown trout Danubian (DA) lineage. Genetic diversity of Caspian brown trout in Iranian Rivers is comparable to the levels usually observed in sustainable anadromous European brown trout populations. Microsatellite data suggested two main clusters connected by gene flow among river basins likely by anadromous fish. No genetic differences were detected between the hatchery sample and the remaining wild populations. While the current hatchery program has not produced detectable genetic changes in the wild populations, conservation strategies prioritizing habitat improvement and recovering natural spawning areas for enhancing wild populations are emphasized.

Complete mitochondrial control region sequences indicate a distinct variety of brown trout Salmo trutta in the Aral Sea

Complete sequencing of the mtDNA control region (CR) from five specimens of brown trout Salmo trutta from the Amu Darya River identified two novel haplotypes belonging to the Danubian lineage. This finding supports the long-standing hypothesis that brown trout in the Aral Sea represent a distinct genetic stock and also illustrates the benefits that complete sequencing of the CR can provide for elucidating phylogeographic relationships.

Presence of unexpected phylogenetic lineages of brown trout Salmo trutta L. in Gacka River, Croatia

This study provides the first analysis of mtDNA control region variation of brown trout samples from the Gacka River, in order to assess their phylogenetic lineage affliation and address the question of the origin of phylogenetic haplotypes in the river. Aligned sequences from 21 individuals were sorted into two haplotypes. Based on the 334 bp fragment at the 50'end of the control region, 14 fish were assigned to the Danubian lineage (67%) and seven were assigned to the AT lineage (33%). All fish assigned to the Danubian lineage revealed just one haplotype: Da2 (M97975). The same was observed within the AT lineage-assigned fish, where only one haplotype, At1 (M97969), was found.The prevalence of Danubian haplotype and no finding of Adriatic haplotype imply an autochthonous status of the Danubian haplotype in Gacka River.

Trout (Salmo trutta) mitochondrial DNA polymorphism in the centre of the marble trout distribution area

The marble trout, a lineage of the Salmo trutta complex, is endemic to the Southern Alpine region. Although it is endangered throughout its entire distribution range, population genetic data were lacking for the central area, including the upper Etsch/Adige River system (South Tyrol, Northern Italy). A total of 672 Salmo trutta specimens, comprising phenotypic marble trout and phenotypic brown trout, from 20 sampling sites throughout South Tyrol were analysed by sequencing the complete mitochondrial DNA control region. Thirteen distinct haplotypes were identified, which clustered within three major genetic lineages: the Marmoratus (MA), the Atlantic (AT) and the Danubian (DA) lineage. 41.7% of the investigated individuals carried haplotypes of the MA lineage, 47.9% of the AT lineage and 10.4% of the DA lineage. It is noticeable that AT haplotypes were present at all sampling sites and no “pure” marble trout population with exclusively MA haplotypes was found. This points to a considerable impact of stocking with allochthonous brown trout, given that there is no evidence for natural colonisation by individuals of the AT lineage. However, our data indicate, for at least four localities, a limited gene flow between the native marble trout and hatchery-reared strains. Future conservation and rehabilitation measures will thus have to concentrate on the identification of remnant pure marble trout individuals from such mixed populations.

Genetic admixture of burbot (Teleostei: Lota lota) in Lake Constance from two European glacial refugia

The burbot, Lota lota, is the only freshwater species of the codfish family and has a Holarctic distribution. Pleistocene glaciations caused significant geographical differentiation in the past, but its life history characterized by winter spawning migrations over large distances is likely to homogenize populations by contemporary gene flow. We investigated the population genetic structure of 541 burbots from Lake Constance and adjacent Rhine and Danube tributaries in Europe using the entire mitochondrial DNA (mtDNA) control region and 11 microsatellites. Microsatellites revealed considerable population divergence (F(ST) = 0.26) and evidenced recent bottlenecks in two Central European rivers. In accordance to previous evidence two main phylogeographic lineages (Atlantic and Danubian) were found co-occurring at similar frequencies in Lake Constance, where they currently undergo random mating as indicated by microsatellites. The Danubian lineage contributed only a small proportion to the lake's mtDNA diversity, and probably expanded within the lake shortly after its formation approximately 10,000-15,000 BP. The larger Atlantic haplotype diversity suggested a population expansion older than the lake itself. Levels of admixture at microsatellite loci were less obvious due to their high variability, and coalescence methods were used to estimate past admixture proportions. Our results reinforce a model of a two-step colonization of Europe by burbot from an ancestral Danubian refuge, and confirm the persistence of a secondary Atlantic refuge, as proposed to exist for other freshwater fish. We conclude that the present-day burbot population in Lake Constance bears the genetic signature of both contemporary gene flow and historical separation events.

Distribution of non-native trout in Slovenia and their introgression with native trout populations as observed through microsatellite DNA analysis

In Slovenia, the Adriatic basin inhabited by native marble trout ( S. marmoratus), and the Danubian basin inhabited by native Danubian lineage of brown trout ( S. trutta) have been intensively affected by stocking with non-native trout strains. In order to assess spread of non-native strains and their introgression with native trout, a population study based on five microsatellite loci was applied across ten marble and ten brown trout populations, ranging from allegedly non-introgressed to heavily managed. On the basis of correspondence analysis, which revealed three clear groupings consisting of the Danubian and Atlantic lineages of brown trout and the marble trout, the alleles, characteristic of each grouping were identified and used for estimating genetic composition of each population according to the three possible origins. Among the wild populations, five marble and one brown trout populations were found to be pure; all the others were introgressed with exotic alleles (Atlantic and marmoratus alleles in the Danubian basin and Atlantic and Danubian in the Adriatic basin) that markedly dominate in intensively managed populations. As revealed by non-significant F IS values, panmixia between native and introduced fishes has for the most part already been reached. Our research showed that it is not only marble trout whose identity is endangered in Slovenia but also the existence of autochthonous Danubian brown trout is critically compromised, which is new information to be taken into account for local trout conservation.