Speciation in the parthenogenetic oribatid mite genus Tectocepheus (Acari, Oribatida) as indicated by molecular phylogeny

Despite the lack of universal concepts for species and speciation, both sexual and asexual organisms are expected to diversify into discrete genotypic and morphological clusters. Species-rich clusters of parthenogenetic oribatid mites likely evolved in the absence of sexual reproduction. We used nucleotide sequences of the large and small rDNA genes (18S and 28S) and the coding genes for heat shock protein 82 (hsp82) and elongation factor-1 alpha (ef-1α) for phylogenetic analyses of three morphotypes of the parthenogenetic oribatid mite genus Tectocepheus. DNA sequence divergences of the different morphotypes were similar to those of sexual species in other organisms. Maximum likelihood analyses of single genes and combined data sets were largely congruent in reconstructing the phylogeny of the Tectocepheus species. The results suggest that the different morphotypes of Tectocepheus indeed evolved in the absence of sexual reproduction, and that Tectocepheus minor, Tectocepheus velatus and Tectocepheus sarekensis are best considered distinct species. Further, the results suggest that 18S rDNA, hsp82 and ef-1α are powerful markers for resolving phylogenetic relationships of oribatid mites. Saturation plots indicated that the D3-region of 28S is much more saturated than all other examined genes. This indicates that the D3-region is unsuitable for resolving ancient splits in oribatid mites.     

Release of nonexchangeable NH4-N after planting of ryegrass in relation to soil content and as affected by nitrate supply

The uptake of N by ryegrass grown in pot culture on a range of soils differing widely in content of nonexchangeable NH₄-N (topsoils: 117 to 354 mg kg^?1 soil; subsoils: 117 to 270 mg kg^?1 soil) was measured to indicate whether the amounts of NH₄-N released from clay minerals were correlated with soil NH₄-N. After two cuts soil analysis revealed that the amounts of mobilized nonexchangeable NH₄-N were between 3.5 and 25.2 mg kg^?1 from topsoils and between 0 and 8.2 mg kg^?1 from subsoils. There was no correlation between soil nonexchangeable NH₄-N content and release. The NH₄-N extracted with 1 N HCl and the actual N uptake of the plants correlated highly significant. Assuming that the whole of the NH₄-N released was taken up by ryegrass, NH₄-N accounted for 11.2 to 75.0% of total N uptake from topsoils and 0 to 37.3% from subsoils. The release of nonexchangeable NH₄-N was increased by the application of nitrate.     

Earthworms as drivers of the competition between grasses and legumes

Grasses and legumes are grown together worldwide to improve total herbage yield and the quality of forage, however, the causes of population oscillations of grasses and legumes are poorly understood. Especially in grasslands, earthworms are among the most important detritivore animals functioning as ecosystem engineers, playing a key role in nutrient cycling and affecting plant nutrition and growth. The objectives of the present greenhouse experiment were to quantify the effects of earthworms on grass–legume competition in model grassland systems at two harvesting dates – simulating the widespread biannual mowing regime in Central European grasslands.The presence of earthworms increased the productivity of grasses and legumes after 6 weeks but only that of grasses after another 10 weeks. In mixed treatments, the presence of grasses and earthworms decreased legume shoot biomass, the amount of nitrogen (N) in shoot tissue and the number of legume flowerheads while the presence of legumes and earthworms increased the amount of N in grass shoots and the infestation of grasses with aphids. Analyses of ¹⁵N/¹⁴N ratios indicate that, compared to legumes, grasses more efficiently exploit soil mineral N and benefit from legume presence through reduced “intra-functional group” competition. In contrast to previous experiments, we found no evidence for N transfer from legumes to grasses. However, legume presence improved total herbage and N yield.Earthworms likely modulate the competition between grasses and legumes by increasing soil N uptake by plants and thereby increasing the competitive strength of grasses. Earthworms function as essential driving agents of grass–legume associations by (I) increasing grass yield, (II) increasing the amount of N in grass hay, (III) increasing the infestation rate of grasses with aphids, and (IV) potentially reducing the attractiveness of grass–legume associations to pollinators.     

Insight into the distribution of arabinoxylans, endoxylanases, and endoxylanase inhibitors in industrial wheat roller mill streams

To gain insight into the distribution of arabinoxylans (AX), endoxylanases, and endoxylanase inhibitors in industrial wheat roller milling, all streams, that is, 54 flour fractions, 4 bran fractions, and the germ, were analyzed for ash, starch, and protein contents, alpha-amylase activity levels, total (TOT-AX) and water-extractable arabinoxylan (WE-AX) contents, endoxylanase activity levels, and endoxylanase inhibitor (TAXI and XIP) contents. In general, bran fractions were significantly richer in TOT-AX and WE-AX contents, endoxylanase activity levels, and endoxylanase inhibitor contents than germ and, even more so, than flour fractions. In the 54 different flour fractions, minimal and maximal values for TOT-AX and WE-AX contents differed by ca. 2-fold, whereas they differed by ca. 15-fold for endoxylanase activity levels. The latter were positively correlated with ash and negatively correlated with starch content, suggesting that the endoxylanase activity in flour is strongly influenced by the level of bran contamination. TAXI contents in the flour fractions varied ca. 4-fold and were strongly correlated with bran-related parameters such as ash content and enzyme activity levels, whereas XIP contents varied ca. 3-fold and were not correlated with any of the parameters measured in this study. The results can be valuable in blending and optimizing wheat flour fractions to obtain flours with specific technological and nutritional benefits.     

Little effect of forest age on oribatid mites on the bark of trees

This study investigates the effect of forest age (20-, 50-, 160-year-old, and primeval forest) on oribatid mite communities on the bark of oak trees in the National Park Pusza Białowieża in eastern Poland. We hypothesized that oribatid mite diversity on bark peaks at forests of intermediate age and that the number of parthenogenetic species of oribatid mites is highest in young stands. In contrast to these hypotheses, the diversity, density, number of juveniles, community structure and the mode of reproduction of oribatid mite species were not significantly affected by forest age. None of the oribatid mite species occurred exclusively on trees of a specific age. The results suggest that oribatid mite communities on the bark of trees are minimally affected by tree harvesting regimes. In contrast to oribatid mites in soil, communities on bark appear to be less sensitive to disturbances.     

Validation of topsoil texture derived from agricultural soil maps by current dense soil sampling

Agricultural soil maps were created to facilitate the management of fields. Such maps, at very large scale (1:5000), cover almost the entire agricultural land in Poland. These maps can be very useful for precision field management. However, they were prepared about 40–50 years ago using old mapping techniques with mainly field (organoleptic) examination of soil. For this reason it is necessary to verify agreement between such maps with the current soil status. In the case of detection of disagreements it is important to identify the causes and propose methods for improving soil maps. Only few studies were made in this aspect. The soil texture (ST) of the upper layer, as presented on the agricultural soil maps from the 1960s and 1970s, was compared with the actual ST of the same four fields in northern and central Poland. For laboratory ST determination, soil samples were collected in a dense sampling network. On average, the agreement of the ST presented on the agricultural soil maps and determined in this study was classified as medium for three fields and good for one field. However, the presence of field areas with poor agreement between the ST determined in this study and that shown on the agricultural maps was detected in all investigated fields. Identified causes for this comprised imprecision of ST determination using the organoleptic method, the generalization of the soil quality maps, and erosion processes during the years between soil mapping and this investigation. The improvement of ST presentation on the large scale soil maps might be achieved by quite denser soil sampling for ST analysis supported by ECa, yield and NDVI maps.     

The formation of terrestrial food webs in glacier foreland: Evidence for the pivotal role of decomposer prey and intraguild predation

We investigated the structure of invertebrate food webs at three glacier foreland sites of an age of 2-34, ca. 60 and ca. 120 years in the European Alps at 2250-2450 m asl. The trophic structure was investigated by analyzing stable isotope ratios of ¹⁵N/¹⁴N and ¹³C/¹²C. The results suggest that the formation of terrestrial food webs during early primary succession heavily relies on prey out of the decomposer system with Collembola being most important. The diet of decomposers likely is based predominantly on allochthonous humus material blown in by wind and deposited by the retreating glacier. Irrespective of the successional stage the animal community consisted mainly of generalist predators with a number of species occurring at each of the successional stages. The results suggest that terrestrial food web formation is associated with a prolongation of food chains caused mainly by predator species switching their diet to include other predators, i.e. by intraguild predation. This suggests that generalist predators, such as cursorial spiders, carabid beetles, harvestman and centipedes, switch prey and include other predators if these are becoming more abundant, i.e. if ecosystems become more productive. Intraguild predation results in complex food webs with high linkage density which likely affects food web functioning and stability.     

Use of isotope-labeled aflatoxins for LC-MS/MS stable isotope dilution analysis of foods

Aflatoxins are a group of very carcinogenic mycotoxins that can be found on a wide range of food commodities including nuts, cereals, and spices. In this study, the first LC-MS/MS stable isotope dilution assay (SIDA) for the determination of aflatoxins in foods was developed. The development of this method was enabled by easily accessible isotope-labeled (deuterated) aflatoxins B2 and G2, which were synthesized by catalytic deuteration of aflatoxin B1 and G1, purified, and well-characterized by NMR and MS. All four aflatoxins of interest (B1, B2, G1, and G2) were quantified in food samples by using these two labeled internal standards. The response factors (RF) of the linear calibrations were revealed to be matrix independent for labeled aflatoxin B2/aflatoxin B2 and labeled aflatoxin G2/aflatoxin G2. For labeled aflatoxin B 2/aflatoxin B 1 and labeled aflatoxin B2/aflatoxin G1 matrix-matched calibration was performed for the model matrices almonds and wheat flour, showing significant differences of the RFs. Limits of detection (LOD) were determined by applying a statistical approach in the presence of the two model matrices, yielding 0.31 microg/kg (aflatoxin B1), 0.09 microg/kg (aflatoxin B2), 0.38 microg/kg (aflatoxin G1), and 0.32 microg/kg (aflatoxin G2) for almonds (similar LODs were obtained for wheat flour). Recovery rates were between 90 and 105% for all analytes. Coefficients of variation (CV) of 12% (aflatoxin B1), 3.6% (aflatoxin B2), 14% (aflatoxin G1), and 4.8% (aflatoxin G2) were obtained from interassay studies. For further validation, a NIST standard reference food sample was analyzed for aflatoxins B1 and B2. The method was successfully applied to determine trace levels of aflatoxins in diverse food matrices such as peanuts, nuts, grains, and spices. Aflatoxin contents in these samples ranged from about 0.5 to 6 microg/kg.     

Kinetics of a bioactive compound (caffeine) mobility at the vicinity of the mechanical glass transition temperature induced by gelling polysaccharide

An investigation of the diffusional mobility of a bioactive compound (caffeine) within the high-solid (80.0% w/w) matrices of glucose syrup and κ-carrageenan plus glucose syrup exhibiting distinct mechanical glass transition properties is reported. The experimental temperature range was from 20 to -60 °C, and the techniques of modulated differential scanning calorimetry, small deformation dynamic oscillation in shear, and UV spectrometry were employed. Calorimetric and mechanical measurements were complementary in recording the relaxation dynamics of high-solid matrices upon controlled heating. Predictions of the reaction rate theory and the combined WLF/free volume framework were further utilized to pinpoint the glass transition temperature (T(g)) of the two matrices in the softening dispersion. Independent of composition, calorimetry yielded similar T(g) predictions for both matrices at this level of solids. Mechanical experimentation, however, was able to detect the effect of adding gelling polysaccharide to glucose syrup as an accelerated pattern of vitrification leading to a higher value of T(g). Kinetic rates of caffeine diffusion within the experimental temperature range were taken with UV spectroscopy. These demonstrated the pronounced effect of the gelling κ-carrageenan/glucose syrup mixture to retard diffusion of the bioactive compound near the mechanical T(g). Modeling of the diffusional mobility of caffeine produced activation energy and fractional free-volume estimates, which were distinct from those of the carbohydrate matrix within the glass transition region. This result emphasizes the importance of molecular interactions between macromolecular matrix and small bioactive compound in glass-related relaxation phenomena.