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Reliable information on past and present vegetation is important to project future changes, especially for rapidly transitioning areas such as the boreal treeline. To study past vegetation, pollen analysis is common, while current vegetation is usually assessed by field surveys. Application of detailed sedimentary DNA (sedDNA) records has the potential to enhance our understanding of vegetation changes, but studies systematically investigating the power of this proxy are rare to date. This study compares sedDNA metabarcoding and pollen records from surface sediments of 31 lakes along a north-south gradient of increasing forest cover in northern Siberia (Taymyr peninsula) with data from field surveys in the surroundings of the lakes. sedDNA metabarcoding recorded 114 plant taxa, about half of them to species level, while pollen analyses identified 43 taxa, both exceeding the 31 taxa found by vegetation field surveys. Increasing Larix percentages from north to south were consistently recorded by all three methods and principal component analyses based on percentage data of vegetation surveys and DNA sequences separated tundra from forested sites. Comparisons of the ordinations using procrustes and protest analyses show a significant fit among all compared pairs of records. Despite similarities of sedDNA and pollen records, certain idiosyncrasies, such as high percentages of Alnus and Betula in all pollen and high percentages of Salix in all sedDNA spectra, are observable. Our results from the tundra to single-tree tundra transition zone show that sedDNA analyses perform better than pollen in recording site-specific richness (i.e., presence/absence of taxa in the vicinity of the lake) and perform as well as pollen in tracing vegetation composition.
In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.
Multidirectional communicative interactions in social networks can have a profound effect on mate choice behavior. Male Atlantic molly Poecilia mexicana exhibit weaker mating preferences when an audience male is presented. This could be a male strategy to reduce sperm competition risk: interacting more equally with different females may be advantageous because rivals might copy mate choice decisions. In line with this hypothesis, a previous study found males to show a strong audience effect when being observed while exercising mate choice, but not when the rival was presented only before the choice tests. Audience effects on mate choice decisions have been quantified in poeciliid fishes using association preference designs, but it remains unknown if patterns found from measuring association times translate into actual mating behavior. Thus, we created five audience treatments simulating different forms of perceived sperm competition risk and determined focal males' mating preferences by scoring pre-mating (nipping) and mating behavior (gonopodial thrusting). Nipping did not reflect the pattern that was found when association preferences were measured, while a very similar pattern was uncovered in thrusting behavior. The strongest response was observed when the audience could eavesdrop on the focal male's behavior. A reduction in the strength of focal males' preferences was also seen after the rival male had an opportunity to mate with the focal male's preferred mate. In comparison, the reduction of mating preferences in response to an audience was greater when measuring association times than actual mating behavior. While measuring direct sexual interactions between the focal male and both stimulus females not only the male's motivational state is reflected but also females' behavior such as avoidance of male sexual harassment.
A competitive immunoassay to detect a hapten using an enzyme-labelled peptide mimotope as tracer
(2002)
Mimotope peptides-peptides which mimic the binding of a hapten to its corresponding monoclonal antibody-were conjugated to peroxidase and used in competitive immunoassay. The established immunoassay was used to quantitatively determine the concentration of hapten. As model system in all the experiments described here, we used the binding of the monoclonal antibody B13-DE1 to fluorescein and the corresponding peptide mimotope.
Home range estimation is routine practice in ecological research. While advances in animal tracking technology have increased our capacity to collect data to support home range analysis, these same advances have also resulted in increasingly autocorrelated data. Consequently, the question of which home range estimator to use on modern, highly autocorrelated tracking data remains open. This question is particularly relevant given that most estimators assume independently sampled data. Here, we provide a comprehensive evaluation of the effects of autocorrelation on home range estimation. We base our study on an extensive data set of GPS locations from 369 individuals representing 27 species distributed across five continents. We first assemble a broad array of home range estimators, including Kernel Density Estimation (KDE) with four bandwidth optimizers (Gaussian reference function, autocorrelated‐Gaussian reference function [AKDE], Silverman's rule of thumb, and least squares cross‐validation), Minimum Convex Polygon, and Local Convex Hull methods. Notably, all of these estimators except AKDE assume independent and identically distributed (IID) data. We then employ half‐sample cross‐validation to objectively quantify estimator performance, and the recently introduced effective sample size for home range area estimation ( N̂ area
) to quantify the information content of each data set. We found that AKDE 95% area estimates were larger than conventional IID‐based estimates by a mean factor of 2. The median number of cross‐validated locations included in the hold‐out sets by AKDE 95% (or 50%) estimates was 95.3% (or 50.1%), confirming the larger AKDE ranges were appropriately selective at the specified quantile. Conversely, conventional estimates exhibited negative bias that increased with decreasing N̂ area. To contextualize our empirical results, we performed a detailed simulation study to tease apart how sampling frequency, sampling duration, and the focal animal's movement conspire to affect range estimates. Paralleling our empirical results, the simulation study demonstrated that AKDE was generally more accurate than conventional methods, particularly for small N̂ area. While 72% of the 369 empirical data sets had >1,000 total observations, only 4% had an N̂ area >1,000, where 30% had an N̂ area <30. In this frequently encountered scenario of small N̂ area, AKDE was the only estimator capable of producing an accurate home range estimate on autocorrelated data.
Environmental heterogeneity is a major determinant of plant population dynamics. In semi-arid Kalahari savannas, heterogeneity is created by savanna structure, i.e. by the spatial arrangement and temporal dynamics of woody plant and open grassland microsites. We formulate a conceptual model describing the effects of savanna dynamics on the population dynamics of the animal-dispersed shrub Grewia flava. From empirical results we derive model rules describing effects of savanna structure on several processes in Grewia's life cycle. By formulating the model, we summarise existing information on Grewia demography and identify gaps in this knowledge. Despite a number of such gaps, the model can be used to make certain quantitative predictions. As an example, we apply the model to investigate the role of seed dispersal in Grewia encroachment on rangelands. Model results show that cattle promote encroachment by depositing substantial numbers of seeds in open areas, where Grewia is otherwise dispersal-limited. Finally, we draw some general conclusions about Grewia's life history and population dynamics. Under natural conditions, concentrated seed deposition under woody plants appears to be a key process causing the observed association between Grewia and other woody plants. Furthermore, low rates of recruitment and high adult survival result in slow-motion dynamics of Grewia populations. As a consequence, Grewia populations interact with savanna dynamics on long temporal and short to intermediate spatial scales.
Apoptotic death of cells damaged by genotoxic stress requires regulatory input from surrounding tissues. The C. elegans scaffold protein KRI-1, ortholog of mammalian KRIT1/CCM1, permits DNA damage-induced apoptosis of cells in the germline by an unknown cell non-autonomous mechanism. We reveal that KRI-1 exists in a complex with CCM-2 in the intestine to negatively regulate the ERK-5/MAPK pathway. This allows the KLF-3 transcription factor to facilitate expression of the SLC39 zinc transporter gene zipt-2.3, which functions to sequester zinc in the intestine. Ablation of KRI-1 results in reduced zinc sequestration in the intestine, inhibition of IR-induced MPK-1/ERK1 activation, and apoptosis in the germline. Zinc localization is also perturbed in the vasculature of krit1(-/-) zebrafish, and SLC39 zinc transporters are mis-expressed in Cerebral Cavernous Malformations (CCM) patient tissues. This study provides new insights into the regulation of apoptosis by cross-tissue communication, and suggests a link between zinc localization and CCM disease.
Exendin-4 is a pharmaceutical peptide used in the control of insulin secretion. Structural information on exendin-4 and related peptides especially on the level of quaternary structure is scarce. We present the first published association equilibria of exendin-4 directly measured by static and dynamic light scattering. We show that exendin-4 oligomerization is pH dependent and that these oligomers are of low compactness. We relate our experimental results to a structural hypothesis to describe molecular details of exendin-4 oligomers. Discussion of the validity of this hypothesis is based on NMR, circular dichroism and fluorescence spectroscopy, and light scattering data on exendin-4 and a set of exendin-4 derived peptides. The essential forces driving oligomerization of exendin-4 are helix–helix interactions and interactions of a conserved hydrophobic moiety. Our structural hypothesis suggests that key interactions of exendin-4 monomers in the experimentally supported trimer take place between a defined helical segment and a hydrophobic triangle constituted by the Phe22 residues of the three monomeric subunits. Our data rationalize that Val19 might function as an anchor in the N-terminus of the interacting helix-region and that Trp25 is partially shielded in the oligomer by C-terminal amino acids of the same monomer. Our structural hypothesis suggests that the Trp25 residues do not interact with each other, but with C-terminal Pro residues of their own monomers.
Diagnostics of Autoimmune Diseases involve screening of patient samples for containing autoantibodies against various antigens. To ensure quality of diagnostic assays a calibrator is needed in each assay system. Different calibrators as recombinant human monoclonal antibodies as well as chimeric antibodies against the autoantigens of interest are described. A less cost-intensive and also more representative possibility covering different targets on the antigens is the utilization of polyclonal sera from other species. Nevertheless, the detection of human autoantibodies as well as the calibration reagent containing antibodies from other species in one assay constitutes a challenge in terms of assay calibration. We therefore developed a cross-reactive monoclonal antibody which binds human as well as rabbit sera with similar affinities in the nanomolar range. We tested our monoclonal antibody S38CD11B12 successfully in the commercial Serazym (R) Anti-Cardiolipin-beta 2-GPI IgG/IgM assay and could thereby prove the eligibility of S38CD11B12 as detection antibody in autoimmune diagnostic assays using rabbit derived sera as reference material.
Ten square-based pyramidal molybdenum complexes with different sulfur donor ligands, that is, a variety of dithiolenes and sulfides, were prepared, which mimic coordination motifs of the molybdenum cofactors of molybdenum-dependent oxidoreductases. The model compounds were investigated by Mo K-edge X-ray absorption spectroscopy (XAS) and (with one exception) their molecular structures were analyzed by X-ray diffraction to derive detailed information on bond lengths and geometries of the first coordination shell of molybdenum. Only small variations in Mo=O and Mo-S bond lengths and their respective coordination angles were observed for all complexes including those containing Mo(CO)(2) or Mo(mu-S)(2)Mo motifs. XAS analysis (edge energy) revealed higher relative oxidation levels in the molybdenum ion in compounds with innocent sulfur-based ligands relative to those in dithiolene complexes, which are known to exhibit noninnocence, that is, donation of substantial electron density from ligand to metal. In addition, longer average Mo-S and Mo=O bonds and consequently lower.(Mo=O) stretching frequencies in the IR spectra were observed for complexes with dithiolene-derived ligands. The results emphasize that the noninnocent character of the dithiolene ligand influences the electronic structure of the model compounds, but does not significantly affect their metal coordination geometry, which is largely determined by the Mo(IV) or (V) ion itself. The latter conclusion also holds for the molybdenum site geometries in the oxidized Mo-VI cofactor of DMSO reductase and the reduced Mo-IV cofactor of arsenite oxidase. The innocent behavior of the dithiolene molybdopterin ligands observed in the enzymes is likely to be related to cofactor-protein interactions.
A cytoplasmically inherited chlorophyll-deficient mutant of barley (Hordeum vulgare) termed cytoplasmic line 3 (CL3), displaying a viridis (homogeneously light-green colored) phenotype, has been previously shown to be affected by elevated temperatures. In this article, biochemical, biophysical, and molecular approaches were used to study the CL3 mutant under different temperature and light conditions. The results lead to the conclusion that an impaired assembly of photosystem I (PSI) under higher temperatures and certain light conditions is the primary cause of the CL3 phenotype. Compromised splicing of ycf3 transcripts, particularly at elevated temperature, resulting from a mutation in a noncoding region (intron 1) in the mutant ycf3 gene results in a defective synthesis of Ycf3, which is a chaperone involved in PSI assembly. The defective PSI assembly causes severe photoinhibition and degradation of PSII.
The phase behavior of a dendritic amphiphile containing a Newkome-type dendron as the hydrophilic moiety and a cholesterol unit as the hydrophobic segment is investigated at the air-liquid interface. The amphiphile forms stable monomolecular films at the airliquid interface on different subphases. Furthermore, the mineralization of calcium phosphate beneath the monolayer at different calcium and phosphate concentrations versus mineralization time shows that at low calcium and phosphate concentrations needles form, whereas flakes and spheres dominate at higher concentrations. Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron diffraction confirm the formation of calcium phosphate. High-resolution transmission electron microscopy and electron diffraction confirm the predominant formation of octacalcium phosphate and hydroxyapatite. The data also indicate that the final products form via a complex multistep reaction, including an association step, where nano-needles aggregate into larger flake-like objects.
Sightings and migration patterns of 65 bean and 65 white-fronted geese are reported. These geese were tagged and serologically screened. 19 of the 53 birds sighted had serologic evidence of Newcastle Disease. The migration patterns of the wild geese provided further evidence that the main resting and wintering sites of migratory waterfowl are likely to be important for the inter- and intraspecies transmission of avian diseases.
In order to explore the behavioral mechanisms underlying aggregation of foragers on local resource patches, it is necessary to manipulate the location, quality and quantity of food patches. This requires careful control over the conditions in the foraging arena, which may be a challenging task in the case of aquatic resource-consumer systems, like that of freshwater zooplankton feeding on suspended algal cells. We present an experimental tool designed to aid behavioral ecologists in exploring the consequences of resource characteristics for zooplankton aggregation behavior and movement decisions under conditions where the boundaries and characteristics (quantity and quality) of food patches can be standardized. The aggregation behavior of Daphnia magna and D. galeata x hyalina was tested in relation to i) the presence or absence of food or ii) food quality, where algae of high or low nutrient (phosphorus) content were offered in distinct patches. Individuals of both Daphnia species chose tubes containing food patches and D. galeata x hyalina also showed a preference towards food patches of high nutrient content. We discuss how the described equipment complements other behavioral approaches providing a useful tool to understand animal foraging decisions in environments with heterogeneous resource distributions.
A direct competitive homogeneous immunoassay for progesterone - the Redox Quenching Immunoassay
(2012)
A direct competitive amperometric immunoassay format for the detection of haptens and proteins was developed. The method is based on the quenching of electroactivity of ferrocenium, which is coupled to the antigen and used as the primary reporter, upon binding to a monoclonal anti-ferrocenium antibody, which is coupled to the detection antibody and used as a secondary reporter. A separation-free progesterone immunoassay with a lower detection limit of 1 ng?mL-1 (3.18 nmol?L-1) in 1?:?2 diluted blood serum was realised by combining two bifunctional conjugates, a ferrocenium-PEG-progesterone tracer and a bioconjugate of one anti-progesterone and one anti-ferrocenium antibody. The immune complex is formed within 30 s upon addition of progesterone, resulting in a total analysis time of 1.5 min.
The uptake of resources from the environment is a vital process for all organisms. Many experimental studies have revealed that the rate at which this process occurs depends critically on the resource concentration, a relationship called "functional response." However, whether the concentration of the consumer normally affects the functional response has been the subject of a long-standing, predominantly theoretical, debate in ecology. Here we present an experimental test between the alternative hypotheses that food uptake depends either only on the resource concentration or on both the resource and the consumer concentrations. In short-term laboratory experiments, we measured the uptake of radioactively labeled, unicellular green algae (Monoraphidium minutum, resource) by the rotifer Brachionus calyciflorus (a consumer) for varying combinations of resource and consumer concentrations. We found that the food uptake by Brachionus depended on the algal concentration with the relationship best described by a Holling type 3 functional response. We detected significant consumer effects on the functional response only at an extraordinarily high Brachionus density (similar to 125 rotifers/mL), which by far exceeds concentrations normally encountered in the field. We conclude that con sumer-dependent food uptake by planktonic rotifers is a phenomenon that can occur under extreme conditions, but probably plays a minor role in natural environments
A drop of immunity
(2021)