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1.
Two Orthotrichum species of the subgenus Orthophyllum were compared with other representatives of this genus using the internally transcribed spacer regions 1 and 2, the chloroplast trnH-psbA region and ISSR and ISJ DNA markers. The applied DNA markers revealed many bands and mutations specific only to O. gymnostomum and O. obtusifolium. A phylogenetic analysis clearly supported the previous concepts postulating that species of the subgenus Orthophyllum should be recognized as separate genus Nyholmiella. 相似文献
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Elevationally biased avian predation as a contributor to the spatial distribution of geometrid moth outbreaks in sub‐arctic mountain birch forest 下载免费PDF全文
ADAM A. PEPI OLE PETTER L. VINDSTAD MALIN EK JANE U. JEPSEN 《Ecological Entomology》2017,42(4):430-438
1. Population dynamics and interactions that vary over a species' range are of particular importance in the context of latitudinal clines in biological diversity. Winter moth (Operophtera brumata) and autumnal moth (Epirrita autumnata) are two species of eruptive geometrids that vary widely in outbreak tendency over their range, which generally increases from south to north and with elevation. 2. The predation pressure on geometrid larvae and pupae over an elevational gradient was tested. The effects of background larval density and bird occupancy of monitoring nest boxes on predation rates were also tested. Predation on larvae was tested through exclusion treatments at 20 replicate stations over four elevations at one site, while pupae were set out to measure predation at two elevations at three sites. 3. Larval densities were reduced by bird predation at three lower elevations, but not at the highest elevation, and predation rates were 1.9 times higher at the lowest elevation than at the highest elevation. The rate of predation on larvae was not related to background larval density or nest box occupancy, although there were more eggs and chicks at the lowest elevation. There were no consistent differences in predation on pupae by elevation. 4. These results suggest that elevational variation in avian predation pressure on larvae may help to drive elevational differences in outbreak tendency, and that birds may play a more important role in geometrid population dynamics than the focus on invertebrate and soil predators of previous work would suggest. 相似文献
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We describe methods for studying axo-dendritic projections, one of the forms of neural connection involved in the complex circuits of the central nervous system, including brainstem auditory pathways. This form of neural connection is often difficult to visualize by conventional tract tracing techniques. Retrogradely identified cells were filled intracellularly with a mixture of fluorescent Lucifer yellow and nonfluorescent HRP in live slice preparations to reveal the detailed morphological features of these cells with special attention to the distal dendrite that may receive projections from suspected or known input axons. Extracellular or intracellular labeling of cells with axons that project to the distal dendrite of the identified cells was accomplished in the same live slice preparation. Using a live slice rather than a fixed slice allows accurate, visually controlled placement of anterograde tracer, which requires living axons for transport, into the source of input to the identified cells within the slice. Live slices also permit one to characterize the identified cells electrophysiologically. Intracellular labeling of cells in a potential source of local input to the identified cells also provides conclusive information concerning with connections of the cells involved. 相似文献
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Elvis K. Tiburu Lalit Deshmukh David R. Janero 《Biochemical and biophysical research communications》2009,384(2):243-4798
We detail the structure and dynamics of a synthetic peptide corresponding to transmembrane helix 6 (TMH6) of human cannabinoid receptor-2 (hCB2) in biomembrane-mimetic environments. The peptide’s NMR structural biology is characterized by two α-helical domains bridged by a flexible, nonhelical hinge region containing a highly-conserved CWFP motif with an environmentally sensitive, Pro-based conformational switch. Buried within the peptide’s flexible region, W258 may hydrogen-bond with L255 to help stabilize the Pro-kinked hCB2 TMH6 structure and position C257 advantageously for interaction with agonist ligands. These characteristics of hCB2 TMH6 are potential structural features of ligand-induced hCB2 activation in vivo. 相似文献
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FRÉDÉRIC JIGUET RICHARD D. GREGORY VINCENT DEVICTOR RHYS E. GREEN PETR VOŘÍŠEK ARCO VAN STRIEN DENIS COUVET 《Global Change Biology》2010,16(2):497-505
Temperate species are projected to experience the greatest temperature increases across a range of modelled climate change scenarios, and climate warming has been linked to geographical range and population changes of individual species at such latitudes. However, beyond the multiple modelling approaches, we lack empirical evidence of contemporary climate change impacts on populations in broad taxonomic groups and at continental scales. Identifying reliable predictors of species resilience or susceptibility to climate warming is of critical importance in assessing potential risks to species, ecosystems and ecosystem services. Here we analysed long‐term trends of 110 common breeding birds across Europe (20 countries), to identify climate niche characteristics, adjusted to other environmental and life history traits, that predict large‐scale population changes accounting for phylogenetic relatedness among species. Beyond the now well‐documented decline of farmland specialists, we found that species with the lowest thermal maxima (as the mean spring and summer temperature of the hottest part of the breeding distribution in Europe) showed the sharpest declines between 1980 and 2005. Thermal maximum predicted the recent trends independently of other potential predictors. This study emphasizes the need to account for both land‐use and climate changes to assess the fate of species. Moreover, we highlight that thermal maximum appears as a reliable and simple predictor of the long‐term trends of such endothermic species facing climate change. 相似文献
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The purpose of these studies is to determine the intermolecular distances that define the location, orientation, and conformation of 2-AG in palmitoyl-oleoyl-phosphatidylcholine (POPC) lipid bilayers using rotational-echo double-resonance (REDOR) NMR. All five protons on the glycerol backbone of 2-AG were replaced with 2H and the distance between the deuterons and naturally occurring 31P on the POPC lipid headgroup determined with REDOR. To determine the distance from each deuteron to the phosphorus, the POPC headgroup was arranged in a hexagonal array. The 2-AG intercalates between the lipid molecules and the 2H labels, resulting in an average distance of z directly above or below the center of the parallelogram of the four phosphorus atoms P1, P2, P3, and P4. For different z values, the 2H–31P inter-nuclear distances were 7.6–9.1 Å (2H–31P1 and 2H–31P31) and 4.4–6.7 Å (2H–31P2 and 2H–31P4). Each result involved the calculations and summation of 893,101 terms. Based on the curve-fitting parameters, the calculations with z = 0 fits the data the best, which means these methylene 2H atoms are at the same level as the phosphate group of the POPC lipid bilayer. Molecular dynamic simulation data suggested that the 2H atoms at the glycerol backbone of 2-AG are involved in an extended H-bonding network with the phosphorus atoms after 10-ns simulation. 相似文献