1,720,983 research outputs found
Anwendung der Genetik im aquatischen Artenschutz: Fokus Marmorierte Forelle
No full textThe Mediterranean freshwater fish biodiversity is in sharp decline, being threatened by several anthropogenic stressors. Among these, the introduction of non-native taxa plays an important negative role, clearly visible in the Northern Adriatic district, where endemic marble trout is heavily impacted by Atlantic brown trout via hybridisation and genetic introgression. In contrast to the situation in the Slovenian Soca River drainage, Northern Italian populations are probably all hybridised. Against this background, genetic screening is crucial in fisheries management actions, such as supportive breeding and stocking. Here, we underline the utility of genetic screening by presenting novel multilocus microsatellite data of Northern Italian marble trout populations. First, we unravel significant subpopulation structure even at the microgeographic level. Second, we point to complex scenarios of genetic introgression in the wild, where the reliable selection of suitable marble trout spawners necessitates from complete genetic control to avoid the propagation of hybridised specimens in the hatchery environment. Such a propagation would be particularly ominous when applying multiple generation captive breeding as evidenced by a realistic simulation case study. Finally, we outline a catalogue of best practice, implemented in fisheries management in South Tyrol since 2016
Supportive breeding program of Marble trout (Salmo marmoratus) in the Province of Bolzano - Italy
Full text linkThe marble trout populations of the Northern Adriatic basin are threatened by human
mediated hybridisation with exotic brown trout. Therefore, conservation measures are urgently needed to counteract further hybridization of this endemic species. The novel supportive breeding program described in this poster, applied within the Province of Bolzano since 2016, aims to conserve the genetic integrity of marble trout, while avoiding both domestication effects and the reduction of effective population size. Local wild marble trout spawners, selected by a genetic screening of each single individual, constitute the basis of the program. To minimize a potential reduction of effective population size induced by supportive breeding, full or partial factorial crossing is conducted. The main part of fertilized eggs is stocked back into the rivers of origin. However, currently it is also a necessary measure to hatch a fraction of the descendants of each trout family under semi-natural conditions. This is done in order to increase the number of available parental fish, and further to be able to provide adequate quantities of fertilised eggs, used for stocking in artificial nests of all river stretches. The genetic screening of wild marble trout (N=578 in 2018) showed a significant hybridization for 80 percent of the phenotypically preselected spawners. The elevated degree of genetic introgression is hampering the here described supportive breeding programs, since it will be more and more difficult to maintain sufficient number of breeders and, in general, pose a serious threat for the conservation of the species within the area of interes
Genetics of the genus Salmo in Italy: evolutionary history, population structure, molecular ecology and conservation
No full textThe Italian peninsula harbours a complex arrangement of native taxa within the genus Salmo, shaped by colonisation routes, palaeo-hydrology and ecological adaptation. In addition, salmonid biodiversity has massively been altered by anthropogenic translocation of non-native trout, thus promoting biotic homogenisation and introgressive hybridisation. Herein, we summarise present knowledge upon relevant colonisation hypotheses and propose that beyond the most likely original advent of Mediterranean salmonids through east to west migration, also subsequent counterdirected migration routes and even in situ evolutionary clade formation might have contributed to Italian trout biodiversity. We then focus on ‘peninsular’ and ‘marble’ lineages as the major native salmonid entities in Italy. Both lineages are constituted by a mosaic of sympatric and parapatric (meta)populations in riverine and lacustrine environments. Insights into molecular ecology of marble trout (Salmo marmoratus) and Lake Garda's carpione (Salmo carpio) are reported as prominent Italian examples. We focus on the problem of exotic brown trout in Italy, including biotic homogenisation and introgressive hybridisation as the negative consequences of this invasion. An attempt towards the definition of management units (MU) among Italian populations, obligatory for sustainable salmonid conservation, closes this chapter
Nothing but a trace left? Autochthony and conservation status of Northern Adriatic Salmo trutta inferred from PCR multiplexing, mtDNA control region sequencing and microsatellite analysis
No full textPhylogeny of Northern Adriatic Salmo trutta is still not resolved, leading to taxonomic controversies and hindering reasonable conservation and fisheries management. We report on the genetic screening of 467 brown trout from 25 sites within Adige, Brenta and Po River drainage basins (Italy). Our main aim was to identify native (Adriatic) brown trout within the central part of the Northern Adriatic area. D-loop lineage screening evidenced a predominance of the Atlantic clade with a frequency of 0.87, followed by the Marmoratus clade with 0.11, and, finally, the Adriatic clade with a frequency of 0.02. The Adriatic clade was found exclusively in specimens from Pianetti River and was represented by haplotype Adcs1. However, microsatellite-based analysis of population structure within Pianetti River specimens failed to identify Adriatic brown trout, but pointed to a nuclear genomic replacement of the former by Atlantic strains. In conjunction with earlier phylogenetic studies, our results contrast with a present-day widespread distribution scenario of Adriatic brown trout within the Northern Adriatic region. From a conservation viewpoint, the punctiform occurrence of Adriatic haplotypes, their ambiguous provenance, and, finally, the presumable genomic replacement at the nuclear genetic level, might hinder reasonable conservation actions and call for revised fisheries management guidelines
Good news for conservation: mitochondrial and microsatellite DNA data detect limited genetic signatures of inter-basin fish transfer in Thymallus thymallus (Salmonidae) from the Upper Drava River
No full textIn the last few decades, numerous populations of European grayling,
Thymallus thymallus, have been suffering from
stocking-induced genetic admixture of foreign strains into wild populations. Concordantly,
genetic introgression was also reportedfor grayling stocks inhabiting the Upper Drava
River, but all published genetic data based on specimens caught at least a decade ago,
when stocking load was strong. Here, we applied mitochondrial control region sequencing
and nuclear microsatellite genotyping to Upper Drava grayling fry collections and
reference samples to update patterns and extent of human-mediated introgression. In
contrast to previous data, we highlighted an almost genetic integrity of Drava grayling,
evidencing limited genetic signatures of trans-basin stocking for grayling of Northern
Alpine Danubian origin. Recent hybridisation was detected only twice among sixty-nine
samples, while several cases of later-generation hybrids were disclosed by linking
mitochondrial sequence to nuclear genetic data. The observed past, but very limited recent
genetic introgression in grayling from Upper Drava seems to reflect shifting stocking
trends, changing from massive introduction of trans-basin fish to more
conservation-oriented strategies during the last 27 years. In a conservation context, we
encourage pursuing the use of local wild grayling for supportive- and captive-breeding,
but underline the need for genetic approaches in brood-stock selection programs. Finally,
our integrated results from sibship reconstruction validate our strictly fry-based
sampling scheme, thus offering a reasonable alternative also for other rheophilic fish
species with similar life-history characteristics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Nothing but a trace left? Autochthony and conservation status of Northern Adriatic Salmo trutta inferred from PCR multiplexing, mtDNA control region sequencing and microsatellite analysis
No full textPhylogeny of Northern Adriatic Salmo trutta is still not resolved, leading to taxonomic controversies and hindering reasonable conservation and fisheries management. We report on the genetic screening of 467 brown trout from 25 sites within Adige, Brenta and Po River drainage basins (Italy). Our main aim was to identify native (Adriatic) brown trout within the central part of the Northern Adriatic area. D-loop lineage screening evidenced a predominance of the Atlantic clade with a frequency of 0.87, followed by the Marmoratus clade with 0.11, and, finally, the Adriatic clade with a frequency of 0.02. The Adriatic clade was found exclusively in specimens from Pianetti River and was represented by haplotype Adcs1. However, microsatellite-based analysis of population structure within Pianetti River specimens failed to identify Adriatic brown trout, but pointed to a nuclear genomic replacement of the former by Atlantic strains. In conjunction with earlier phylogenetic studies, our results contrast with a present-day widespread distribution scenario of Adriatic brown trout within the Northern Adriatic region. From a conservation viewpoint, the punctiform occurrence of Adriatic haplotypes, their ambiguous provenance, and, finally, the presumable genomic replacement at the nuclear genetic level, might hinder reasonable conservation actions and call for revised fisheries management guidelines
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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