Are forests potential landscape barriers for foraging bumblebees? Landscape scale experiments with Bombus terrestris agg. and Bombus pascuorum (Hymenoptera, Apidae)

Habitat fragmentation is generally considered to have detrimental effects on insect movement and associated pollen flow between plant populations. Against this background the role of forests as potential barriers for foraging bumblebees of the species Bombus terrestris agg. and Bombus pascuorum was studied in different experiments. Bombus terrestris agg. workers were found foraging at distances of up to 2.2 km from their nests. B. terrestris agg. as well as B. pascuorum individuals crossed 600 m of forestland between floral mass resources (Phacelia tanacetifolia, Helianthus annuus), although in general a high degree of site fidelity was observed. B. pascuorum workers accepted artificial floral resources within the forest, whereas the minor use of resources below forest canopy observed for B. terrestris agg. possibly indicates a preference for direct forage flights, probably leading above the forest canopy. Our results warn against experiments with genetically modified crop species with potential bumblebee pollination (e.g. Brassica napus), in which an isolating effect of forests is assumed.     

Biodegradation of humic substances by microscopic filamentous fungi: chromatographic and spectroscopic proxies

Purpose

The study of interactions between humic substances (HSs) and soil filamentous fungi is the key to understanding the sustainable soil functioning. The present work aims to examine the decomposition of HSs by filamentous dark-pigmented fungus Alternaria alternatа under the laboratory conditions and to determine the effect of easily assimilable organic carbon on this process. Analyzing such polydisperse substances like HSs by a complex integrated methodology makes it possible to explore the data on their decomposition by microorganisms.

Materials and methods

To achieve the aforementioned goals, we used chromatographic and spectroscopic approaches: low-pressure size-exclusion and hydrophobic interaction chromatography accompanied by absorption and fluorescence spectroscopy. To determine the effect cometabolism conditions produced on HS decomposition, two types of carbon substrates were added to the nutrient media: easily assimilable organic carbon (standard 0.3% or reduced 0.03% sucrose content) and hardly assimilable organic carbon (HSs), as well as their combinations. Five HS samples of different organic matter origin have been inspected: potassium humates (HPs) and humic acids (HAs) from coal, peat, and lignosulfonate. Correlation matrix and principal component analysis (PCA) were calculated for comprehensive data analysis.

Results and discussion

Transformations of the investigated HSs under fungal cultivation lead to the increase in the low molecular weight fraction, rise of hydrophilic fraction, enlargement of absorbance ratio A₂₅₀/A₃₆₅, shortening of the emission wavelength of the humic-type fluorescence, and growth in the fluorescence quantum yield measured with excitation at 355 nm. A positive correlation was observed between the accumulation of fungal biomass and the degree of HS decomposition. PCA analysis confirms that the difference in the results of HS decomposition largely depends on the sucrose content and the nature of HSs. We divided all the HS samples into four groups according to the degree of HS decomposition: original HS solutions, HPs altered using fungal cultivation at 0.03% sucrose, HAs after fungal cultivation at 0.03% sucrose, and finally, HSs (both HPs and HAs) after fungal cultivation at 0.3% sucrose.

Conclusions

In the laboratory experiments, we showed that (1) the isolated HAs were more effectively degraded than the parent HPs, and this process was more pronounced at a reduced sucrose content, and (2) the decomposition of stable organic compounds (HSs) was activated by the easily assimilable carbon sources (especially 0.3% sucrose) being present. We assume that it is the easily assimilable organic carbon that most likely triggers the HS degradation working as the priming effect in natural environments.

     

Suitability of weed species prevailing in Spanish vineyards as hosts for root-knot nematodes

Commercial vineyards in southern Spain were surveyed and sampled during October to December 2004 to determine the extent to which common weeds present were suitable hosts of root-knot nematodes infesting soils of those vineyards. Seven weed species commonly growing in grapevine soils in southern Spain were found infected by either Meloidogyne incognita or M. javanica: Amaranthus retroflexus (redroot pigweed), Anchusa azurea (ox-tongue), Chenopodium album (goosefoot), Erodium moschatum (musk stork’s bill), Malva rotundifolia (low mallow), Sinapis alba (white mustard), and Solanum nigrum (black nightshade). The host suitability of the weeds to root-knot nematodes was evaluated on the basis of root galling severity and nematode population densities in soil and roots. Also, the host–parasite relationship in these naturally Meloidogyne-infected weeds was examined. All the weed species in the study were considered suitable hosts for M. incognita and M. javanica because: (a) high Meloidogyne spp. populations occurred in roots and surrounding soil of the weed species; (b) the severity of root galling was high, and (c) well-established permanent feeding sites were observed in the histopathological studies of infected root tissues. In addition, this study presents the first reports of S. alba and A. azurea as hosts for M. incognita, and of E. moschatum as a new host for M. javanica, thus increasing the list of reported weed hosts for Meloidogyne spp. These results indicate that noticeable population densities of M. incognita and M. javanica can be maintained or increased in these weeds, at population levels higher than those previously reported for the same nematodes infecting grapevine roots. The weeds infesting vineyards thus represent an important source of inoculum of Meloidogyne spp., and furthermore may act as reservoirs of these nematodes which can be disseminated within or among vineyards by agricultural operations.     

Long-term evaluation of yield components of young olive trees during the onset of fruit production under different irrigation regimes

A four-year study was conducted on young Olea europaea L. trees to investigate the effect of deficit irrigation starting from the onset of fruit production. Subsurface drip irrigation was used to supply 100% (FI), 46–52% (DI), or 2–6% (SI) of tree water needs. Tree growth was reduced by deficit irrigation, whereas, return bloom was not. Per tree fruit yield of DI trees was 68% that of FI, but fruit yield efficiency based on tree size was similar between treatments. Fruit set and the number of fruits of FI trees were similar to those of DI trees and significantly higher than in SI trees. No significant differences in fruit fresh weight were found between FI and DI. The oil yield and oil yield efficiency of the DI treatment were 82 and 110% that of FI trees, respectively. A level of about 50% deficit proved sustainable to irrigate trees for oil production.     

Genetic variability and molecular evolution of arabis mosaic virus based on the coat protein gene sequence

Arabis mosaic virus (ArMV) is an important pathogen infecting a wide range of plant species worldwide. In the present study, we carried out exhaustive phylogenetic analyses based on the coat protein (CP) sequence of ArMV isolates originating from different host plants and geographic regions. Maximum-likelihood reconstruction revealed the presence of three distinct, well-supported phylogroups. BaTS analyses indicated that the diversity of ArMV isolates may be correlated with both host plant and geographic origin. Moreover, population genetic analyses showed significant differences in the level of genetic diversity among variants within ArMV that originated from rhubarb plants, as expected by quasispecies. Further analysis revealed that both selection and recombination are shaping the population structure of ArMV. In total 14 groups of residues were detected as coevolving for different amino acid properties.     

Structural Influence on Photooxidative Degradation of Halogenated Phenols

The influence of structure on degradation of five halogenated phenols (XPs) by UV/H₂O₂ process was investigated. The combined influence of type or number of substituents and UV/H₂O₂ process parameters (pH and [H₂O₂]) on the degradation kinetics of 2-fluorophenol (2-FP), 2-chlorophenol (2-CP), 2-bromophenol (2-BP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) was studied using modified miscellaneous 3³ full factorial design and response surface modeling (RSM). Studied XPs obey first-order degradation kinetics within the investigated range of process parameters. Determined degradation rate constants (k _obs) were correlated with process and structural parameters by the quadratic polynomial models. Analysis of variance (ANOVA) demonstrated RSM models’ accuracy and showed that, in addition to pH and [H₂O₂], model terms related with the pollutant structure are highly influential. k _obs of mono-XPs follow the decreasing order 2-FP, 2-CP, and 2-BP, while CPs follow the decreasing order 2-CP, 2,4-DCP, and 2,4,6-TCP. Biodegradability (biochemical oxygen demand (BOD)₅/chemical oxygen demand (COD)) and toxicity (TU) were evaluated prior to the treatment and at the reference time intervals. The observed differences are correlated with the structural characteristics of studied XPs.     

Membrane proteins of the endoplasmic reticulum induce high-curvature tubules

The tubular structure of the endoplasmic reticulum (ER) appears to be generated by integral membrane proteins, the reticulons and a protein family consisting of DP1 in mammals and Yop1p in yeast. Here, individual members of these families were found to be sufficient to generate membrane tubules. When we purified yeast Yop1p and incorporated it into proteoliposomes, narrow tubules (approximately 15 to 17 nanometers in diameter) were generated. Tubule formation occurred with different lipids; required essentially only the central portion of the protein, including its two long hydrophobic segments; and was prevented by mutations that affected tubule formation in vivo. Tubules were also formed by reconstituted purified yeast Rtn1p. Tubules made in vitro were narrower than normal ER tubules, due to a higher concentration of tubule-inducing proteins. The shape and oligomerization of the "morphogenic" proteins could explain the formation of the tubular ER.     

Interactions between fawns and does of farmed fallow deer Dama dama in the postnatal period

The aim of the present study was to describe the suckling behavior of the offspring of farmed European fallow deer Dama dama in the postnatal period. Video surveillance footage from the first 18 days postpartum was analyzed in detail to reveal that the duration of interactions between the mother and the offspring changed with the fawns’ age. The duration of mother‐offspring interactions was longest between postpartum days 12 and 18. The frequency of interactions at different times of the day varied in the analyzed periods. The results of the study could be used to increase the welfare of farmed deer.     

Diminishing reciprocal fairness by disrupting the right prefrontal cortex

Humans restrain self-interest with moral and social values. They are the only species known to exhibit reciprocal fairness, which implies the punishment of other individuals' unfair behaviors, even if it hurts the punisher's economic self-interest. Reciprocal fairness has been demonstrated in the Ultimatum Game, where players often reject their bargaining partner's unfair offers. Despite progress in recent years, however, little is known about how the human brain limits the impact of selfish motives and implements fair behavior. Here we show that disruption of the right, but not the left, dorsolateral prefrontal cortex (DLPFC) by low-frequency repetitive transcranial magnetic stimulation substantially reduces subjects' willingness to reject their partners' intentionally unfair offers, which suggests that subjects are less able to resist the economic temptation to accept these offers. Importantly, however, subjects still judge such offers as very unfair, which indicates that the right DLPFC plays a key role in the implementation of fairness-related behaviors.     

Molecular evolution of tomato black ring virus and de novo generation of a new type of defective RNAs during long-term passaging in different hosts

Tomato black ring virus (TBRV) is a worldwide-distributed RNA virus infecting a wide range of different host plants, including crop species, trees, shrubs, and weeds. Here, we investigated the molecular evolution of TBRV and its adaptability to different plant species. The TBRV-Pi isolate was used to generate five independent evolution lineages serially passaged in either quinoa, tobacco, or tomato plants. After 15 passages, the genetic variability present in all the lineages was characterized for the movement (MP) and coat (CP) coding cistrons. We addressed two main questions: to what extent does the amount of genetic variability in the TBRV genome depend on the host species, and are there host species-specific adaptive mutations? Overall, 201 different nucleotide substitutions emerged during the evolution experiment, with some of them appearing multiple times in different lineages; two of them (one in CP and one in MP) were unique for a particular host plant. We have shown that the degree of genetic differentiation depends on the host species in which the virus evolved, and that positive selection is operating upon certain residues, particularly in CP. Moreover, we have characterized new types of defective RNAs that arose during the TBRV-Pi evolution in tobacco. Furthermore, this is the first report of a defective RNA from the RNA2 of TBRV.