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1. The increase of species richness with the area of the habitat sampled, that is the species–area relationship, and its temporal analogue, the species–time relationship (STR), are among the few general laws in ecology with strong conservation implications. However, these two scale‐dependent phenomena have rarely been considered together in biodiversity assessment, especially in freshwater systems. 2. We examined how the spatial scale of sampling influences STRs for a Central‐European stream fish assemblage (second‐order Bernecei stream, Hungary) using field survey data in two simulation‐based experiments. 3. In experiment one, we examined how increasing the number of channel units, such as riffles and pools (13 altogether), and the number of field surveys involved in the analyses (12 sampling occasions during 3 years), influence species richness. Complete nested curves were constructed to quantify how many species one observes in the community on average for a given number of sampling occasions at a given spatial scale. 4. In experiment two, we examined STRs for the Bernecei fish assemblage from a landscape perspective. Here, we evaluated a 10‐year reach level data set (2000–09) for the Bernecei stream and its recipient watercourse (third‐order Kemence stream) to complement results on experiment one and to explore the mechanisms behind the observed patterns in more detail. 5. Experiment one indicated the strong influence of the spatial scale of sampling on the accumulation of species richness, although time clearly had an additional effect. The simulation methodology advocated here helped to estimate the number of species in a diverse combination of spatial and temporal scale and, therefore, to determine how different scale combinations influence sampling sufficiency. 6. Experiment two revealed differences in STRs between the upstream (Bernecei) and downstream (Kemence) sites, with steeper curves for the downstream site. Equations of STR curves were within the range observed in other studies, predominantly from terrestrial systems. Assemblage composition data suggested that extinction–colonisation dynamics of rare, non‐resident (i.e. satellite) species influenced patterns in STRs. 7. Our results highlight that the determination of species richness can benefit from the joint consideration of spatial and temporal scales in biodiversity inventory surveys. Additionally, we reveal how our randomisation‐based methodology may help to quantify the scale dependency of diversity components (α, β, γ) in both space and time, which have critical importance in the applied context. 相似文献
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Michael D Kennedy Mark J Haykowsky Carol A Boliek Ben TA Esch Jessica M Scott Darren ER Warburton 《Dynamic medicine : DM》2006,5(1):8
Background
Near infrared spectroscopy (NIRS) is used to assess muscle oxygenation (MO) within skeletal muscle at rest and during aerobic exercise. Previous investigations have used a single probe placement to measure MO during various forms of exercise. However, regional MO differences have been shown to exist within the same muscle which suggests that different areas of the same muscle may have divergent MO. Thus, the aim of this study was to examine whether regional differences in MO exist within the same muscle during different types of incremental (rest, 25, 50, 75, 100 % of maximum) exercise (1 leg knee extension (KE), 2 leg KE, or cycling).Methods
Nineteen healthy active males (Mean ± SD: Age 27 ± 4 yrs; VO2max: 55 ± 11 mL/kg/min) performed incremental exercise to fatigue using each mode of exercise. NIRS probes were placed on the distal and proximal portion of right leg vastus lateralis (VL). Results were analyzed with a 3-way mixed model ANOVA (probe × intensity × mode).Results
Differences in MO exist within the VL for each mode of exercise, however these differences were not consistent for each level of intensity. Comparison of MO revealed that the distal region of VL was significantly lower throughout KE exercise (1 leg KE proximal MO – distal MO = 9.9 %; 2 leg KE proximal MO – distal MO = 13 %). In contrast, the difference in MO between proximal and distal regions of VL was smaller in cycling and was not significantly different at heavy workloads (75 and 100 % of maximum).Conclusion
MO is different within the same muscle and the pattern of the difference will change depending on the mode and intensity of exercise. Future investigations should limit conclusions on MO to the area under assessment as well as the type and intensity of exercise employed.5.
Morgan AW Robinson JI Barrett JH Martin J Walker A Babbage SJ Ollier WE Gonzalez-Gay MA Isaacs JD 《Arthritis research & therapy》2006,8(4):R109-6
The Fc gamma receptors have been shown to play important roles in the initiation and regulation of many immunological and
inflammatory processes and to amplify and refine the immune response to an infection. We have investigated the hypothesis
that polymorphism within the FCGR genetic locus is associated with giant cell arteritis (GCA). Biallelic polymorphisms in FCGR2A, FCGR3A, FCGR3B and FCGR2B were examined for association with biopsy-proven GCA (n = 85) and healthy ethnically matched controls (n = 132) in a well-characterised cohort from Lugo, Spain. Haplotype frequencies and linkage disequilibrium (D') were estimated across the FCGR locus and a model-free analysis performed to determine association with GCA. There was a significant association between
FCGR2A-131RR homozygosity (odds ratio (OR) 2.10, 95% confidence interval (CI) 1.12 to 3.77, P = 0.02, compared with all others) and carriage of FCGR3A-158F (OR 3.09, 95% CI 1.10 to 8.64, P = 0.03, compared with non-carriers) with susceptibility to GCA. FCGR haplotypes were examined to refine the extent of the association. The haplotype showing the strongest association with GCA
susceptibility was the FCGR2A-FCGR3A 131R-158F haplotype (OR 2.84, P = 0.01 for homozygotes compared with all others). There was evidence of a multiplicative joint effect between homozygosity
for FCGR2A-131R and HLA-DRB1*04 positivity, consistent with both of these two genetic factors contributing to the risk of disease. The risk of GCA in
HLA-DRB1*04 positive individuals homozygous for the FCGR2A-131R allele is increased almost six-fold compared with those with other FCGR2A genotypes who are HLA-DRB1*04 negative. We have demonstrated that FCGR2A may contribute to the 'susceptibility' of GCA in this Spanish population. The increased association observed with a FCGR2A-FCGR3A haplotype suggests the presence of additional genetic polymorphisms in linkage disequilibrium with this haplotype that may
contribute to disease susceptibility. These findings may ultimately provide new insights into disease pathogenesis. 相似文献
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Toenshoff ER Kvellestad A Mitchell SO Steinum T Falk K Colquhoun DJ Horn M 《PloS one》2012,7(3):e32696
Epitheliocystis, a disease characterised by cytoplasmic bacterial inclusions (cysts) in the gill and less commonly skin epithelial cells, has been reported in many marine and freshwater fish species and may be associated with mortality. Previously, molecular and ultrastructural analyses have exclusively associated members of the Chlamydiae with such inclusions. Here we investigated a population of farmed Atlantic salmon from the west coast of Norway displaying gill epitheliocystis. Although 'Candidatus Piscichlamydia salmonis', previously reported to be present in such cysts, was detected by PCR in most of the gill samples analysed, this bacterium was found to be a rare member of the gill microbiota, and not associated with the observed cysts as demonstrated by fluorescence in situ hybridization assays. The application of a broad range 16 S rRNA targeted PCR assay instead identified a novel betaproteobacterium as an abundant member of the gill microbiota. Fluorescence in situ hybridization demonstrated that this bacterium, tentatively classified as 'Candidatus Branchiomonas cysticola', was the cyst-forming agent in these samples. While histology and ultrastructure of 'Ca. B. cysticola' cysts revealed forms similar to the reticulate and intermediate bodies described in earlier reports from salmon in seawater, no elementary bodies typical of the chlamydial developmental cycle were observed. In conclusion, this study identified a novel agent of epitheliocystis in sea-farmed Atlantic salmon and demonstrated that these cysts can be caused by bacteria phylogenetically distinct from the Chlamydiae. 相似文献
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Diversity of Bacterial Endosymbionts of Environmental Acanthamoeba Isolates 总被引:1,自引:0,他引:1
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Stephan Schmitz-Esser Elena R. Toenshoff Susanne Haider Eva Heinz Verena M. Hoenninger Michael Wagner Matthias Horn 《Applied microbiology》2008,74(18):5822-5831
Free-living amoebae are frequent hosts for bacterial endosymbionts. In this study, the symbionts of eight novel environmental Acanthamoeba strains isolated from different locations worldwide were characterized. Phylogenetic analysis revealed that they were related to one of four evolutionary lineages of amoeba symbionts recognized previously. This study provides evidence for the existence of only a small number of phylogenetically well-separated groups of obligate intracellular endosymbionts of acanthamoebae with global distribution. 相似文献
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