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951.
The Fucus populations on rocky shores along 300 km of the coastal waters of southeast Sweden in the Baltic proper have been studied since 1984 at a number of fixed sites as part of monitoring programmes. This paper describes changes in distribution and abundance of F. vesiculosus and F. serratus during the period 1984–2001. Sheltered sites showed a consistent temporal and spatial pattern of Fucus spp. distribution over a coastline of 300 kilometres. The depth penetration and abundance of Fucus spp. increased during the 1980s. Around 1990 the development reversed as a consequence of grazing and in 1997 many sites were almost devoid of Fucus spp. Since 1998 both abundance and depth penetration have increased again, possibly as a result of local measures against eutrophication. Exposed sites, on the other hand, lost their Fucus populations at the beginning of the 1990s, and they have not recovered. Extended field studies lead us to deduce that the fixed sites referred to above were representative of the Fucus populations in the area investigated. Major declines, both at sheltered and exposed sites, are attributed to grazing by the isopod Idotea baltica. The populations of I. baltica may have been favoured by the continuing eutrophication of the Baltic, a series of mild winters in the 1990s, and a contemporary decline in some potential predators. 相似文献
952.
Stephen A. Diamond Peter C. Trenham Michael J. Adams Blake R. Hossack Roland A. Knapp Stacey L. Stark David Bradford P. Stephen Corn Ken Czarnowski Paul D. Brooks Dan Fagre Bob Breen Naomi E. Detenbeck Kathy Tonnessen 《Ecosystems》2005,8(5):462-477
Ultraviolet-B radiation (UV-B, 280–320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia
(Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/Kings Canyon
(Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools,
field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose
estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks
was 19.3 W-h m−2 (range of 3.4–32.1 W-h m−2). The mean dose was lowest in Acadia (13.7 W-h m−2) and highest in Rocky (24.4 W-h m−2). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 μW cm−2 (range 21.4–194.7 μW cm−2) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column
UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L−1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%–87 %. DOC concentration, as well
as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape
reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in
UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B
on aquatic organisms. 相似文献
953.
Genetic relatedness in groups is sex-specific and declines with age of helpers in a cooperatively breeding cichlid 总被引:3,自引:0,他引:3
Kin selection can explain the evolution of cooperative breeding and the distribution of relatives within a population may influence the benefits of cooperative behaviour. We provide genetic data on relatedness in the cooperatively breeding cichlid Neolamprologus pulcher. Helper to breeder relatedness decreased steeply with increasing helper age, particularly to the breeding males. Helper to helper relatedness was age‐assortative and also declined with age. These patterns of relatedness could be attributed to territory take‐overs by outsiders when breeders had disappeared (more in breeding males), between‐group dispersal of helpers and reproductive parasitism. In six of 31 groups females inherited the breeding position of their mother or sister. These matrilines were more likely to occur in large groups. We conclude that the relative fitness benefits of helping gained through kin selection vs. those gained through direct selection depend on helper age and sex. 相似文献
954.
Forecasting Environmental Responses to Restoration of Rivers Used as Log Floatways: An Interdisciplinary Challenge 总被引:1,自引:0,他引:1
Christer Nilsson Fabio Lepori Björn Malmqvist Erik Törnlund Niclas Hjerdt James M. Helfield Daniel Palm Johan Östergren Roland Jansson Eva Brännäs Hans Lundqvist 《Ecosystems》2005,8(7):779-800
Log floating in the 19th to mid 20th centuries has profoundly changed the environmental conditions in many northern river
systems of the world. Regulation of flow by dams, straightening and narrowing of channels by various piers and wing dams,
and homogenization of bed structure are some of the major impacts. As a result, the conditions for many riverine organisms
have been altered. Removing physical constructions and returning boulders to the channels can potentially restore conditions
for these organisms. Here we describe the history of log driving, review its impact on physical and biological conditions
and processes, and predict the responses to restoration. Reviewing the literature on comparable restoration efforts and building
upon this knowledge, using boreal Swedish rivers as an example, we address the last point. We hypothesize that restoration
measures will make rivers wider and more sinuous, and provide rougher bottoms, thus improving land-water interactions and
increasing the retention capacity of water, sediment, organic matter and nutrients. The geomorphic and hydraulic/hydrologic
alterations are supposed to favor production, diversity, migration and reproduction of riparian and aquatic organisms. The
response rates are likely to vary according to the types of processes and organisms. Some habitat components, such as beds
of very large boulders and bedrock outcrops, and availability of sediment and large woody debris are believed to be extremely
difficult to restore. Monitoring and evaluation at several scales are needed to test our predictions. 相似文献
955.
Aurelia Lartigue Laurent Drouot Fabienne Jouen Roland Charlionet Fran?ois Tron Danièle Gilbert 《Arthritis research & therapy》2005,7(6):R1394
We showed previously that nucleophosmin (NPM), a nucleolar phosphoprotein, is recognized by sera from (NZW × BXSB)F1 (WB) mice, a model of systemic lupus erythematosus (SLE) and anti-phospholipid syndrome. In the present study we analysed
the prevalence and kinetics of anti-NPM autoantibodies in WB mice by a solid-phase ELISA with recombinant human (rh) NPM as
the antigen and showed that most male WB mouse sera had anti-NPM antibodies that were responsible for their indirect immunofluorescence
staining pattern on Hep-2 cells. Anti-NPM antibodies were significantly associated with anti-cardiolipin (aCL) antibodies.
This antibody profile mirrored that observed in certain human SLE sera because anti-NPM antibodies were detected in 28% of
the sera from patients with SLE and were similarly associated with aCL antibodies. The demonstration that rhNPM bound to cardiolipin
(CL) in vitro and increased the CL-binding activity of a WB-derived aCL monoclonal antibody indicates that NPM can interact with CL to
form SLE-related immunogenic particles that might be responsible for the concomitant production of anti-NPM and aCL antibodies. 相似文献
956.
957.
958.
The macroalgal belt in the southern Baltic Sea may be partly structured by the interaction of physical and biological factors. A field study, spanning the 1990s, describes a rapid decline of the Fucus spp. stands along the wave-exposed Swedish southeast coast. During this period, a relative dominance of Fucus vesiculosus L. shifted to a relative dominance of Fucus serratus L. The decline of F. vesiculosus coincided with observations of large numbers of the grazing isopods Idotea baltica (Pallas) and Idotea granulosa Rathke, or with field observations of frequent grazing marks on Fucus fronds. I. baltica, but not I. granulosa, tended to aggregate in the declining Fucus spp. stands, indicating a strong preference for Fucus spp. In a mesocosm experiment I. baltica, when given a choice, grazed both Fucus species at weak water motion. At strong water motion grazing was concentrated on F. vesiculosus. It is hypothesized that one of the reasons I. baltica preferred F. vesiculosus to F. serratus at strong water motion may have been differences in habitat quality, like width of thallus, influencing the ability to cling to the plant. Smaller thallus, as in F. vesiculosus, thus is the preferred habitat for grazing of I. blatica. We postulate that the existence of F. serratus in the area may be favoured by strong wave action and moderate but not strong grazing by I. baltica, relaxing the interspecific competition from F. vesiculosus. 相似文献
959.
Bernard Chevassus Edwige Quillet Francine Krieg Marie-Gwénola Hollebecq Muriel Mambrini André Fauré Laurent Labbé Jean-Pierre Hiseux Marc Vandeputte 《遗传、选种与进化》2004,36(6):643-661
Growth rate is the main breeding goal of fish breeders, but individual selection has often shown poor responses in fish species. The PROSPER method was developed to overcome possible factors that may contribute to this low success, using (1) a variable base population and high number of breeders (Ne > 100), (2) selection within groups with low non-genetic effects and (3) repeated growth challenges. Using calculations, we show that individual selection within groups, with appropriate management of maternal effects, can be superior to mass selection as soon as the maternal effect ratio exceeds 0.15, when heritability is 0.25. Practically, brown trout were selected on length at the age of one year with the PROSPER method. The genetic gain was evaluated against an unselected control line. After four generations, the mean response per generation in length at one year was 6.2% of the control mean, while the mean correlated response in weight was 21.5% of the control mean per generation. At the 4th generation, selected fish also appeared to be leaner than control fish when compared at the same size, and the response on weight was maximal (≈130% of the control mean) between 386 and 470 days post fertilisation. This high response is promising, however, the key points of the method have to be investigated in more detail. 相似文献
960.
Francine M Perrine Barry G Rolfe Michael F Hynes Charles H Hocart 《Plant Physiology and Biochemistry》2004,42(9):723-729
A new method for preparing alkyl esters of indole-3-acetic acid (IAA) in aqueous solution is adapted from the chloroformate method originally described by Husek for the analysis of amino acids. This method has the significant advantage of avoiding the generation and use of diazomethane, and is done in aqueous solution without the need to dry the sample with concomitant non-specific losses of IAA. The effectiveness of this method is demonstrated by its use in an isotope dilution gas chromatography-mass spectrometry (GC-MS) assay of IAA and L-tryptophan (Trp) in the culture supernatant of a series of Sinorhizobium meliloti and Rhizobium leguminosarum bv. trifolii strains that can interact with rice to either enhance or inhibit rice plant growth. We were testing the hypothesis that the rice growth inhibition was related to the biosynthesis of IAA. It was found that S. meliloti and Rhizobium strains produced high amounts of IAA in Trp supplemented BIII minimal medium compared to BIII media. All the strains produced more than the minimum amount of IAA required to inhibit rice growth and thus IAA is not the major inhibitory factor of rice seedling growth from S. meliloti and Rhizobium strains. 相似文献