共查询到20条相似文献，搜索用时 15 毫秒
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Giuseppina Messina Roberto Cazzolla Gatti Angeliki Droutsa Martina Barchitta Elisa Pezzino Antonella Agodi Bianca Maria Lombardo 《Ecology and evolution》2016,6(1):191-201
Biological diversity analysis is among the most informative approaches to describe communities and regional species compositions. Soil ecosystems include large numbers of invertebrates, among which soil bugs (Crustacea, Isopoda, Oniscidea) play significant ecological roles. The aim of this study was to provide advices to optimize the sampling effort, to efficiently monitor the diversity of this taxon, to analyze its seasonal patterns of species composition, and ultimately to understand better the coexistence of so many species over a relatively small area. Terrestrial isopods were collected at the Natural Reserve “Saline di Trapani e Paceco” (Italy), using pitfall traps monthly monitored over 2 years. We analyzed parameters of α‐ and β‐diversity and calculated a number of indexes and measures to disentangle diversity patterns. We also used various approaches to analyze changes in biodiversity over time, such as distributions of species abundances and accumulation and rarefaction curves. As concerns species richness and total abundance of individuals, spring resulted the best season to monitor Isopoda, to reduce sampling efforts, and to save resources without losing information, while in both years abundances were maximum between summer and autumn. This suggests that evaluations of β‐diversity are maximized if samples are first collected during the spring and then between summer and autumn. Sampling during these coupled seasons allows to collect a number of species close to the γ‐diversity (24 species) of the area. Finally, our results show that seasonal shifts in community composition (i.e., dynamic fluctuations in species abundances during the four seasons) may minimize competitive interactions, contribute to stabilize total abundances, and allow the coexistence of phylogenetically close species within the ecosystem. 相似文献
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- Relatively high β‐diversity among aquatic insect communities inhabiting high‐elevation streams is most commonly presumed to result from increased dispersal limitation between isolated mountaintop ‘islands’. However, these elevational patterns of β‐diversity have been predominately drawn from observed changes in community composition along single‐thread channels, where the downstream increase in habitat size and hydrologic connectivity provides potential alternative explanations.
- In this study, we applied an alternative conceptual ‘tributary model’ to ask whether patterns of aquatic insect β‐diversity in similar‐sized, hydrologically disconnected streams showed a similar elevational gradient in diversity patterns as previously reported for conceptual ‘mainstem model’ studies. Aquatic insects were sampled from 24 low‐order, montane streams that are tributaries to larger rivers in three adjacent catchments spanning c. 2000–3500 m in elevation. We used relative abundance data to quantify two types of β‐diversity: (i) community turnover‐β, or the change in local diversity among adjacent streams along the elevational gradient within each catchment, and (ii) community variation‐β, or the change in local diversity among all streams within three elevation zones combined across catchments.
- Our results provided evidence of no relationship between β‐diversity and elevation in aquatic insect communities in small montane streams. Community turnover‐β was found to be consistently high among sites within catchments and displayed no significant trend across the elevational gradient for any catchment. Community variation‐β showed a nonlinear response to elevation, with sites in the high‐elevation and low‐elevation zones having similarly high community variation‐β compared to sites in the mid‐elevation zone.
- Our ‘tributary model’ results provide the first evidence that β‐diversity among small, isolated streams can have similar turnover rates across broad elevational gradients. Our results also show similar patterns of β‐diversity among low‐ and high‐elevation tributaries, suggesting that dispersal limitation is not restricted to high‐elevation streams.
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《Peptide Science》2017,108(3)
The conformational characteristics of protected homo‐oligomeric Boc‐[β3(R)Val]n‐OMe, n = 1, 2, 3, 4, 6, 9, and 12 have been investigated in organic solvents using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) absorption spectroscopy and circular dichroism (CD) methods. The detailed 1H NMR analysis of Boc‐[β3(R)Val]12‐OMe reveals that the peptide aggregates extensively in CDCl3, but is disaggregated in 20%, (v/v) dimethyl sulfoxide (DMSO) in CDCl3 and in CD3OH. Limited assignment of the N‐terminus NH groups, together with solvent dependence of NH chemical shifts and temperature coefficients provides evidence for 14‐helix conformation in the 12‐residue peptide. FTIR analysis in CHCl3 establishes that the onset of folding and aggregation, as evidenced by NH stretching bands at 3375 cm−1 (intramolecular) and 3285 cm−1 (intermolecular), begins at the level of the tetrapeptide. The observed CD bands, 214 nm (negative) and 198 nm (positive), support 14‐helix formation in the 9 and 12 residue sequences. The folding and aggregation tendencies of homo‐oligomeric α‐, β‐, and γ‐ residues is compared in the model peptides Boc‐[ωVal]n‐NHMe, ω = α, β, and γ and n = 1, 2, and 3. Analysis of the FTIR spectra in CHCl3, establish that the tendency to aggregate at the di and tripeptide level follows the order β > α∼γ, while the tendency to fold follows the order γ > β > α. 相似文献
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Timothée Poisot Elsa Canard David Mouillot Nicolas Mouquet Dominique Gravel 《Ecology letters》2012,15(12):1353-1361
In a context of global changes, and amidst the perpetual modification of community structure undergone by most natural ecosystems, it is more important than ever to understand how species interactions vary through space and time. The integration of biogeography and network theory will yield important results and further our understanding of species interactions. It has, however, been hampered so far by the difficulty to quantify variation among interaction networks. Here, we propose a general framework to study the dissimilarity of species interaction networks over time, space or environments, allowing both the use of quantitative and qualitative data. We decompose network dissimilarity into interactions and species turnover components, so that it is immediately comparable to common measures of β‐diversity. We emphasise that scaling up β‐diversity of community composition to the β‐diversity of interactions requires only a small methodological step, which we foresee will help empiricists adopt this method. We illustrate the framework with a large dataset of hosts and parasites interactions and highlight other possible usages. We discuss a research agenda towards a biogeographical theory of species interactions. 相似文献
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Sigrid Dassen Roeland Cortois Henk Martens Mattias de Hollander George A. Kowalchuk Wim H. van der Putten Gerlinde B. De Deyn 《Molecular ecology》2017,26(15):4085-4098
Plants are known to influence belowground microbial community structure along their roots, but the impacts of plant species richness and plant functional group (FG) identity on microbial communities in the bulk soil are still not well understood. Here, we used 454‐pyrosequencing to analyse the soil microbial community composition in a long‐term biodiversity experiment at Jena, Germany. We examined responses of bacteria, fungi, archaea, and protists to plant species richness (communities varying from 1 to 60 sown species) and plant FG identity (grasses, legumes, small herbs, tall herbs) in bulk soil. We hypothesized that plant species richness and FG identity would alter microbial community composition and have a positive impact on microbial species richness. Plant species richness had a marginal positive effect on the richness of fungi, but we observed no such effect on bacteria, archaea and protists. Plant species richness also did not have a large impact on microbial community composition. Rather, abiotic soil properties partially explained the community composition of bacteria, fungi, arbuscular mycorrhizal fungi (AMF), archaea and protists. Plant FG richness did not impact microbial community composition; however, plant FG identity was more effective. Bacterial richness was highest in legume plots and lowest in small herb plots, and AMF and archaeal community composition in legume plant communities was distinct from that in communities composed of other plant FGs. We conclude that soil microbial community composition in bulk soil is influenced more by changes in plant FG composition and abiotic soil properties, than by changes in plant species richness per se. 相似文献
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Masahiro Nakajima Ryuta Yoshida Akimasa Miyanaga Hayao Taguchi 《Acta Crystallographica. Section F, Structural Biology Communications》2014,70(10):1398-1401
Lin1840 is a putative β‐glucosidase that is predicted to be involved in 1,2‐β‐glucan metabolism since the lin1839 gene encoding a 1,2‐β‐oligoglucan phosphorylase and the lin1840 gene are located in the same gene cluster. Here, Lin1840 was crystallized. The crystals of Lin1840 diffracted to beyond 1.8 Å resolution. The crystal belonged to space group I121, with unit‐cell parameters a = 89.75, b = 95.10, c = 215.00 Å, α = 90.00, β = 96.34, γ = 90.00°. 相似文献
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Qinfeng Guo 《Molecular ecology》2012,21(22):5396-5403
The genetic variation across a species’ range is an important factor in speciation and conservation, yet searching for general patterns and underlying causes remains challenging. While the majority of comparisons between central and marginal populations have revealed a general central–marginal (C–M) decline in genetic diversity, others show no clear pattern. Similarly, most latitudinal studies (although much fewer, especially those conducted rangewide) also showed latitudinal trends in genetic variation. To date, the C–M and latitudinal patterns have often been examined independently and have rarely been considered together when accounting for the observed genetic variation across species ranges. Here, in the light of the most recent findings, I show how latitude might be responsible for some of the deviations from the general C–M trends in genetic diversity, and vice versa. In the future, integrating latitude and range geometry with climate‐induced species migration would offer important insights into conservation prioritization across species ranges. 相似文献
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Nobuo Okazaki Maki Kumei Miho Manzoku Seiki Kuramitsu Mikako Shirouzu Akeo Shinkai Shigeyuki Yokoyama 《Acta Crystallographica. Section F, Structural Biology Communications》2007,63(3):173-177
TTHA0281 is a hypothetical protein from Thermus thermophilus HB8 that belongs to an uncharacterized protein family, UPF0150, in the Pfam database and to COG1598 in the National Center for Biotechnology Information Database of Clusters of Orthologous Groups. The X‐ray crystal structure of the protein was determined by a multiple‐wavelength anomalous dispersion technique and was refined at 1.9 Å resolution to a final R factor of 18.5%. The TTHA0281 monomer adopts an α‐β‐β‐β‐α fold and forms a homotetramer. Based on the properties and functions of structural homologues of the TTHA0281 monomer, the TTHA0281 protein is speculated to be involved in RNA metabolism, including RNA binding and cleavage. 相似文献
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Stefanie Kobus Pablo Perez-Garcia Astrid Hoeppner Nicholas Holzscheck Filip Kovacic Wolfgang R. Streit Karl-Erich Jaeger Jennifer Chow Sander H. J. Smits 《Acta Crystallographica. Section F, Structural Biology Communications》2019,75(4):307-311
The hyperthermophilic crenarchaeon Ignicoccus hospitalis KIN4/I possesses at least 35 putative genes encoding enzymes that belong to the α/β‐hydrolase superfamily. One of those genes, the metallo‐hydrolase‐encoding igni18, was cloned and heterologously expressed in Pichia pastoris. The enzyme produced was purified in its catalytically active form. The recombinant enzyme was successfully crystallized and the crystal diffracted to a resolution of 2.3 Å. The crystal belonged to space group R32, with unit‐cell parameters a = b = 67.42, c = 253.77 Å, α = β = 90.0, γ = 120.0°. It is suggested that it contains one monomer of Igni18 within the asymmetric unit. 相似文献
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Octavio Jiménez‐Robles Juan M. Guayasamin Santiago R. Ron Ignacio De la Riva 《Ecology and evolution》2017,7(8):2489-2500
Assembly of ecological communities is important for the conservation of ecosystems, predicting perturbation impacts, and understanding the origin and loss of biodiversity. We tested how amphibian communities are assembled by neutral and niche‐based mechanisms, such as habitat filtering. Species richness, β‐diversities, and reproductive traits of amphibians were evaluated at local scale in seven habitats at different elevation and disturbance levels in Wisui Biological Station, Morona‐Santiago, Ecuador, on the foothills of the Cordillera del Kutukú; and at regional scale using 109 localities across evergreen forests of Amazonia and its Andean slopes (0–3,900 m a.s.l.). At local scale, species composition showed strong differences among habitats, explained mainly by turnover. Reproductive modes occurred differently across habitats (e.g., prevalence of direct developers at high elevation, where breeding in ground level water disappears). At regional scale, elevation was the most important factor explaining the changes in species richness, reproductive trait occurrences, and biotic dissimilarities. Species number in all groups decreased with elevation except for those with lotic tadpoles and terrestrial reproduction stages. Seasonality, annual precipitation, and relative humidity partially explained the occurrence of some reproductive traits. Biotic dissimilarities were also mostly caused by turnover rather than nestedness and were particularly high in montane and foothill sites. Within lowlands, geographic distance explained more variability than elevation. Habitat filtering was supported by the different occurrence of reproductive traits according to elevation, water availability, and breeding microhabitats at both scales, as well as other assembly mechanisms based in biotic interactions at local scale. Human‐generated land use changes in Amazonia and its Andean slopes reduce local amphibian biodiversity by alteration of primary forests and loss of their microhabitats and the interaction network that maintains their unique amphibian assemblages with different reproductive strategies. 相似文献
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The stress response neuropeptide CRF increases amyloid‐β production by regulating γ‐secretase activity 
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下载免费PDF全文 Hyo‐Jin Park Yong Ran Joo In Jung Oliver Holmes Ashleigh R Price Lisa Smithson Carolina Ceballos‐Diaz Chul Han Michael S Wolfe Yehia Daaka Andrey E Ryabinin Seong‐Hun Kim Richard L Hauger Todd E Golde Kevin M Felsenstein 《The EMBO journal》2015,34(12):1674-1686
The biological underpinnings linking stress to Alzheimer's disease (AD) risk are poorly understood. We investigated how corticotrophin releasing factor (CRF), a critical stress response mediator, influences amyloid‐β (Aβ) production. In cells, CRF treatment increases Aβ production and triggers CRF receptor 1 (CRFR1) and γ‐secretase internalization. Co‐immunoprecipitation studies establish that γ‐secretase associates with CRFR1; this is mediated by β‐arrestin binding motifs. Additionally, CRFR1 and γ‐secretase co‐localize in lipid raft fractions, with increased γ‐secretase accumulation upon CRF treatment. CRF treatment also increases γ‐secretase activity in vitro, revealing a second, receptor‐independent mechanism of action. CRF is the first endogenous neuropeptide that can be shown to directly modulate γ‐secretase activity. Unexpectedly, CRFR1 antagonists also increased Aβ. These data collectively link CRF to increased Aβ through γ‐secretase and provide mechanistic insight into how stress may increase AD risk. They also suggest that direct targeting of CRF might be necessary to effectively modulate this pathway for therapeutic benefit in AD, as CRFR1 antagonists increase Aβ and in some cases preferentially increase Aβ42 via complex effects on γ‐secretase. 相似文献
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Yoshihiro Yamaguchi Genta Sato Yuriko Yamagata Yohei Doi Jun‐ichi Wachino Yoshichika Arakawa Koki Matsuda Hiromasa Kurosaki 《Acta Crystallographica. Section F, Structural Biology Communications》2009,65(6):540-543
The X‐ray crystal structure of AmpC β‐lactamase (AmpCD) with a tripeptide deletion (Gly286‐Ser287‐Asp288) produced by Escherichia coli HKY28, a ceftazidime‐resistant strain, was determined at a resolution of 1.7 Å. The structure of AmpCD suggests that the tripeptide deletion at positions 286–288 located in the H10 helix causes a structural change of the Asn289–Asn294 region from the α‐helix present in the native AmpC β‐lactamase of E. coli to a loop structure, which results in a widening of the substrate‐binding site. 相似文献
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FRANCISCA FUENTES‐RODRÍGUEZ MELCHOR JUAN IRENE GALLEGO MIRIAN LUSI ENCARNACIÓN FENOY DAVID LEÓN PATRICIO PEÑALVER JULIA TOJA J. JESÚS CASAS 《Freshwater Biology》2013,58(1):63-78
1. Agricultural intensification has caused dramatic biodiversity loss in many agricultural landscapes over the last century. Here, we investigated whether new types of farm ponds (made of artificial substrata) in intensive systems and natural‐substratum ponds in traditional farming systems differ in their value for aquatic biodiversity conservation. 2. We analysed the main patterns of environmental variation, compared α‐, β‐ and γ‐diversity of macroinvertebrates between ponds types and evaluated the role of submerged aquatic vegetation (SAV). Generalised additive models (GAM) were used to analyse the relationships of α‐ and β‐diversity with environmental predictors, and variation partitioning to separate the effect of environmental and spatial characteristics on the variation in macroinvertebrate assemblages. Moran’s eigenvector maps (MEMs) were used to define spatial variables. 3. A principal coordinate analysis (PCoA) detected a primary environmental gradient that separated nutrient‐rich ponds from those dominated by SAV; a secondary morphometric gradient distinguished natural‐substratum ponds, with large surface area and structural complexity, from artificial‐substratum ponds with steeper slopes. Natural‐substratum ponds had almost twice the α‐ and γ‐diversity of artificial‐substratum ponds, and diversity significantly increased when SAV was present, particularly in artificial‐substratum ponds. Total phosphorus (TP) strongly contributed to explain the patterns in diversity, while SAV was a significant predictor of assemblage composition and diversity. GAMs revealed optima of both α‐diversity at intermediate SAV covers and β‐diversity at intermediate–high TP concentrations. 4. These findings have important implications for conservation planning. Adaptation of artificial‐substratum ponds by adding natural substratum and smoothing the gradient of pond margins would improve their conservation value. Development of SAV with occasional harvests and certain cautionary measures to control nutrient levels may also improve both the agronomical and environmental function of ponds. 相似文献
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Delineating biogeographical regions is one of the primary steps when analysing biogeographical patterns. In their proposed quantitative framework, Kreft & Jetz (2010, Journal of Biogeography, 37 , 2029–2053) recommended the use of the βsim index to delineate biogeographical regions because this turnover measure is weakly affected by differences in species richness between localities. A recent study by Carvalho et al. (2012, Global Ecology and Biogeography, 21 , 760–771) critiziced the use of βsim in ecological and biogeographical studies, and proposed the β‐3 index. Here we used simple numerical examples and an empirical case study (European freshwater fishes) to highlight potential pitfalls associated with the use of β‐3 for bioregionalization. We show that β‐3 is not a richness‐independent measure of species turnover. We also show that this index violates the ‘complementarity’ property, namely that localities without species in common have the largest dissimilarity, which is an essential prerequisite for beta diversity studies. 相似文献