The concept of habitat specificity revisited     

Rune Halvorsen  Anette Edvardsen 《Landscape Ecology》2009,24(7):851-861

Habitat specificity indices reflect richness (α) and/or distinctiveness (β) components of diversity. The latter may be defined by α and γ (landscape) diversity in two alternative ways: multiplicatively () and additively (). We demonstrate that the original habitat specificity concept of Wagner and Edwards (Landscape Ecol 16:121–131, 2001) consists of three independent components: core habitat specificity (uniqueness of the species composition), patch area and patch species richness. We describe habitat specificity as a family of indices that may include either area or richness components, or none or both, and open for use of different types of mean in calculation of core habitat specificity. Core habitat specificity is a beta diversity measure: the effective number of completely distinct communities in the landscape. Habitat specificity weighted by species number is a gamma diversity measure: the effective number of species that a patch contributes to landscape richness. We compared 12 habitat specificity indices by theoretical reasoning and by use of field data (vascular plant species in SE Norwegian agricultural landscapes). Habitat specificity indices are strongly influenced by weights for patch area and patch species richness, and the relative contribution of rare vs. common species (type of mean). The relevance of properties emphasized by each habitat specificity index for evaluation of patches in a biodiversity context is discussed. Core habitat specificity is emphasized as an ecologically interpretable measure that specifically addresses patch uniqueness while habitat specificity weighted by species number combines species richness and species composition in ways relevant for conservation biological assessment. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

The minimum dietary requirement of vitamin C in Atlantic salmon (Salmo salar) fry using Ca ascorbate-2-monophosphate as dietary source     

Kjartan Sandnes  Ole Torrissen  Rune Waagbø 《Fish physiology and biochemistry》1992,10(4):315-319

The minimum dietary vitamin C requirement for optimal growth and normal development in Atlantic salmon (Salmo salar) fry at the onset of feeding was studied, using Ca ascorbate-2-monophosphate (AP) as dietary source. The requirement was established by means of a feeding study lasting for 23 weeks from the beginning of feeding. The practical diets used were supplemented with AP at levels of 0, 10, 20, 40, 80 and 160 mg ascorbic acid (AA) equivalents/kg. Growth, mortality, hydroxyproline content in skin and backbone, and AA in liver were recorded to evaluate the results. The results suggest that the minimum dietary requirement for optimal growth and normal development is in the range of 10–20 mg AA equivalents/kg dry diet during the period studied.  相似文献   

Immune response and disease resistance in Atlantic salmon (Salmo salar L.) fed three levels of dietary vitamin E and the effect of vaccination on the liver status of antioxidant vitamins   总被引：3，自引：0，他引：3  

Bjarte Lygren  Brit Hjeltnes  Rune Waagbø 《Aquaculture International》2002,9(5):401-411

Atlantic salmon were fed 40, 300 or 1100 mgall-rac--tocopheryl acetate kg feed^–1 for 12 weeks.After 6 weeks half of the fish in each group were marked and vaccinated (i.p.injection) against furunculosis and vibriosis. Liver -tocopherol levelsreflected the dietary input after 6 and 12 weeks of feeding. Noimmunomodulatoryeffects of dietary vitamin E on baseline levels of the immune parameters beforevaccination were detected in this study, as evaluated by antibody dependent andspontaneous plasma complement activities. In general, vaccination increasedplasma complement activities and the number of antigen specific antibodyproducing cells as compared with unvaccinated control fish, but with nodifferences with respect to the vitamin E regimes. Also the ability ofunvaccinated fish to withstand experimental furunculosis was unaffected bydietary vitamin E. The concentrations of -tocopherol and ascorbic acidinthe liver were, however, negatively affected 6 weeks post vaccination comparedto respective unvaccinated fish.  相似文献   

Allelic losses and gains during translocations of a high conservation value fish,Coregonus lavaretus     

Kim Præbel  Colin W. Bean  Jennifer A. Dodd  Elizabeth C. Etheridge  Andrew R.D. Gowans  Rune Knudsen  Alexander A. Lyle  Peter S. Maitland  Ian J. Winfield  Colin E. Adams 《水产资源保护:海洋与淡水生态系统》2021,31(9):2575-2585

1. The use of translocations to establish new or ‘refuge’ populations for species with high conservation value is controversial but widely used in conservation management. One of the risks of this approach is that an establishing population does not adequately capture the genetic diversity of the donor gene pool. This effect, rarely examined, is tested here.
2. In this study the genetic consequences of two conservation translocations after five generations (16 years) of the European whitefish, Coregonus lavaretus, were quantified. Both translocations were made using almost the same genetic groups and thus represent a partly replicated natural study.
3. Analysis of 12 informative microsatellites showed that expected heterozygosity, the mean number of alleles per locus and allelic richness did not differ between donor and translocated populations. There was also no loss of heterozygosity in the translocated populations, nor deviations from Hardy–Weinberg equilibrium expectations, nor signs of linkage disequilibrium.
4. All populations were genetically differentiated but pairwise F_ST values were low, indicating that the magnitude of divergence was small.
5. There was no evidence of inbreeding but there were significant differences in private allelic richness between donor and translocated populations. Of 50 alleles found in the donor population, 16% of the rarer alleles were lost in one translocated population and 8% in the other.
6. Allele loss without a reduction in heterozygosity strongly points to stochastic drift effects having occurred following translocation. The evidence indicates that alleles that were not detected in the donor population have arisen de novo in the translocated populations.
7. It is concluded that conservation translocations comprising even a modest number of propagules can successfully capture a high proportion of genetic variation of the host population, and that reduced genetic variation in the translocated population may be mitigated by the emergence of new variation over short time periods.

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Mycobacterium salmoniphilum infection in farmed Atlantic salmon, Salmo salar L     

Zerihun MA  Nilsen H  Hodneland S  Colquhoun DJ 《Journal of fish diseases》2011,34(10):769-781

Multiple greyish‐white visceral nodules containing abundant rapidly growing and acid‐fast bacteria, subsequently identified as Mycobacterium salmoniphilum, were detected in moribund and newly dead market‐sized fish during a period of increased mortality in an Atlantic salmon, Salmo salar, farm in western Norway. Isolates cultured from diseased fish were phenotypically consistent with Mycobacterium sp. previously isolated from Atlantic salmon [MT 1890 (= NCIMB13533), MT1892, MT1900 and MT1901] in the Shetland Isles, Scotland. Partial sequences of 16S rDNA, ribosomal RNA internal transcribed spacer (ITS1), 65‐kDa heat‐shock protein (Hsp65) and β subunit of RNA polymerase (rpoB) revealed 97‐99% similarity with M. salmoniphilum type strain ATCC 13758^T. The source of infection was not confirmed. Koch’s postulates were fulfilled following experimental challenge of Atlantic salmon with field isolate NVI6598 ( FJ616988 ). Mortality was recorded in experimentally infected fish; however, the infection remained subclinical in the majority of affected fish over the 131‐day challenge period.  相似文献   

Phosphorylation networks regulating JNK activity in diverse genetic backgrounds     

Bakal C  Linding R  Llense F  Heffern E  Martin-Blanco E  Pawson T  Perrimon N 《Science (New York, N.Y.)》2008,322(5900):453-456

Cellular signaling networks have evolved to enable swift and accurate responses, even in the face of genetic or environmental perturbation. Thus, genetic screens may not identify all the genes that regulate different biological processes. Moreover, although classical screening approaches have succeeded in providing parts lists of the essential components of signaling networks, they typically do not provide much insight into the hierarchical and functional relations that exist among these components. We describe a high-throughput screen in which we used RNA interference to systematically inhibit two genes simultaneously in 17,724 combinations to identify regulators of Drosophila JUN NH(2)-terminal kinase (JNK). Using both genetic and phosphoproteomics data, we then implemented an integrative network algorithm to construct a JNK phosphorylation network, which provides structural and mechanistic insights into the systems architecture of JNK signaling.  相似文献   

Protein displacement by DExH/D "RNA helicases" without duplex unwinding     

Fairman ME  Maroney PA  Wang W  Bowers HA  Gollnick P  Nilsen TW  Jankowsky E 《Science (New York, N.Y.)》2004,304(5671):730-734

Members of the DExH/D superfamily of nucleic acid-activated nucleotide triphosphatases are essential for virtually all aspects of RNA metabolism, including pre-messenger RNA splicing, RNA interference, translation, and nucleocytoplasmic trafficking. Physiological substrates for these enzymes are thought to be regions of double-stranded RNA, because several DExH/D proteins catalyze strand separation in vitro. These "RNA helicases" can also disrupt RNA-protein interactions, but it is unclear whether this activity is coupled to duplex unwinding. Here we demonstrate that two unrelated DExH/D proteins catalyze protein displacement independently of duplex unwinding. Therefore, the essential functions of DExH/D proteins are not confined to RNA duplexes but can be exerted on a wide range of ribonucleoprotein substrates.  相似文献   

Molecular biology. When a part is as good as the whole     

deHaseth PL  Nilsen TW 《Science (New York, N.Y.)》2004,303(5662):1307-1308

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Culling prey promotes predator recovery--alternative states in a whole-lake experiment     

Persson L  Amundsen PA  De Roos AM  Klemetsen A  Knudsen R  Primicerio R 《Science (New York, N.Y.)》2007,316(5832):1743-1746

Many top-predator fish stocks in both freshwater and marine systems have collapsed as a result of overharvesting. Consequently, some of these communities have shifted into seemingly irreversible new states. We showed, for predators feeding on prey that exhibit food-dependent growth, that culling of fish prey may promote predator recovery. We removed old stunted individuals of a prey-fish species in a large, low-productive lake, which caused an increase in the availability of small-sized prey and allowed the predator to recover. The shift in community state has been sustained for more than 15 years after the cull ended and represents an experimental demonstration of an alternative stable state in a large-scale field system. Because most animals exhibit food-dependent growth, shifts into alternative stable states resulting from overcompensating prey growth may be common in nature and may require counterintuitive management strategies.  相似文献   

Properties of chalconaringenin and rutin isolated from cherry tomatoes     

Slimestad R  Verheul M 《Journal of agricultural and food chemistry》2011,59(7):3180-3185

Fresh cherry tomatoes cv. 'Susanne' contain more of the two flavonoids chalconaringenin (CN) and rutin than lycopene. Therefore some properties including antioxidant behavior of the flavonoids were studied. The two flavonoids were extracted from peel and isolated by use of different chromatographic methods. Molecular absorbtivities were found to be 26907 for CN and 20328 abs M(-1) cm(-1) for rutin. Both compounds exhibited properties as antioxidants through several assays, and rutin was found to be the strongest antioxidant except in one assay. None of the assays revealed pro-oxidative effects. As naringenin rather than CN is frequently reported as a tomato constituent, the stability of CN was investigated in order to detect potential ways of isomerization during sample preparation. CN isomerized slowly both under UVB radiation and in alkaline solutions. Thus, such factors do not explain the occurrence of naringenin in tomato samples. The deficiency in reports on CN may be explained by the similarity in chromatographic behaviors of CN and naringenin, and due to the fact that they have same molecular weights.  相似文献