Assessing invertebrate herbivory in human‐modified tropical forest canopies

1. Studies on the effects of human‐driven forest disturbance usually focus on either biodiversity or carbon dynamics but much less is known about ecosystem processes that span different trophic levels. Herbivory is a fundamental ecological process for ecosystem functioning, but it remains poorly quantified in human‐modified tropical rainforests.
2. Here, we present the results of the largest study to date on the impacts of human disturbances on herbivory. We quantified the incidence (percentage of leaves affected) and severity (the percentage of leaf area lost) of canopy insect herbivory caused by chewers, miners, and gall makers in leaves from 1,076 trees distributed across 20 undisturbed and human‐modified forest plots in the Amazon.
3. We found that chewers dominated herbivory incidence, yet were not a good predictor of the other forms of herbivory at either the stem or plot level. Chewing severity was higher in both logged and logged‐and‐burned primary forests when compared to undisturbed forests. We found no difference in herbivory severity between undisturbed primary forests and secondary forests. Despite evidence at the stem level, neither plot‐level incidence nor severity of the three forms of herbivory responded to disturbance.
4. Synthesis. Our large‐scale study of canopy herbivory confirms that chewers dominate the herbivory signal in tropical forests, but that their influence on leaf area lost cannot predict the incidence or severity of other forms. We found only limited evidence suggesting that human disturbance affects the severity of leaf herbivory, with higher values in logged and logged‐and‐burned forests than undisturbed and secondary forests. Additionally, we found no effect of human disturbance on the incidence of leaf herbivory.

     

Biological monitoring of exposure to pesticide residues among Belgian florists

Abstract

Many pesticides applied in cut flowers can be readily absorbed through the skin of florists during preparing bouquets and handling contaminated flowers. A study was conducted among volunteer Belgian florists in order to assess their total exposure by measuring concentrations of pesticides (parent compounds and metabolites) in their urines. A total of 42 urine samples (24-h urines) were collected from florists during their professional activities, on the three most important commercial periods. The concentrations of pesticide residues and metabolites in urine samples were analyzed with a multiresidue liquid chromatography tandem mass spectrometry method, after an ethyl acetate extraction. The results are compared with those of a control group of 42 subjects not occupationally exposed to pesticides, collected in the same periods. A total of 70 residues (56 pesticides and 14 metabolites) were identified, with an average of about eight pesticide residues and metabolites per florist’s urine sample and an average total concentration per sample of 4.3 µg/g creatinine, ranging from 0.2 to 67 µg/g creatinine. Significantly higher urinary excretion of metabolites (t-test) was found in florists than in control group. These results demonstrate that Belgian florists are exposed daily to pesticide residues with a potential effect on their health.     

Frequency, timing, extent, and size of winter thaw-refreeze events in Alaska 2001–2008 detected by remotely sensed microwave backscatter data

Creation of ice layers in snow due to thaw-refreeze events can lock away winter forage, preventing access by large mammals and causing population declines. Data are limited, however, on the frequency, timing, extent, and size of thaw-refreeze events in northern latitudes given the area’s remoteness and paucity of weather stations. We used a remote sensing approach to detect thaw-refreeze events in Alaska during winter between 2001 and 2008. We also compared these results to a regional climate reanalysis dataset that identified rain events (freezing and non-freezing rain). All areas of the state, except high elevation sites, had ≥1 thaw-refreeze event during the study period. Southwestern Alaska had the highest frequency of thaw-refreeze events with an average of >4 events each winter, whereas northern Alaska had the lowest frequency with an average of <2 events. We observed substantial inter-annual variation in the distribution and frequency of thaw-refreeze events. For most of the state, thaw-refreeze occurred at similar rates each winter month, except in northern Alaska where thaw-refreeze events were most frequent in early and later winter. The median extent of individual thaw-refreeze events was 469 km², however, events in the interior of the state tended to be larger. Remotely sensed thaw-refreeze detections generally had low correspondence with observations from the climate reanalysis dataset. Our results support the use of remotely sensed data to identify thaw-refreeze events.     

The landscape of metabolic pathway dependencies in cancer cell lines

The metabolic reprogramming of cancer cells creates metabolic vulnerabilities that can be therapeutically targeted. However, our understanding of metabolic dependencies and the pathway crosstalk that creates these vulnerabilities in cancer cells remains incomplete. Here, by integrating gene expression data with genetic loss-of-function and pharmacological screening data from hundreds of cancer cell lines, we identified metabolic vulnerabilities at the level of pathways rather than individual genes. This approach revealed that metabolic pathway dependencies are highly context-specific such that cancer cells are vulnerable to inhibition of one metabolic pathway only when activity of another metabolic pathway is altered. Notably, we also found that the no single metabolic pathway was universally essential, suggesting that cancer cells are not invariably dependent on any metabolic pathway. In addition, we confirmed that cell culture medium is a major confounding factor for the analysis of metabolic pathway vulnerabilities. Nevertheless, we found robust associations between metabolic pathway activity and sensitivity to clinically approved drugs that were independent of cell culture medium. Lastly, we used parallel integration of pharmacological and genetic dependency data to confidently identify metabolic pathway vulnerabilities. Taken together, this study serves as a comprehensive characterization of the landscape of metabolic pathway vulnerabilities in cancer cell lines.     

Structural, metabolic and developmental evaluation of ovulated rabbit oocytes before and after cryopreservation by vitrification and slow freezing

The cryopreservation of oocytes is valuable for the preservation of women's fertility and might also be an interesting tool to preserve animal genetic biodiversity but it is not often used because of the very poor fertility recovered after thawing, especially in rabbit species. The objective of our study was to evaluate the effect of slow-freezing and vitrification on the structural integrity of ovulated rabbit oocytes, their ATP contents, and their developmental competence. Results show that, whatever the method is used, cryopreservation has a dramatic effect on the metabolic integrity, the structural integrity, and the developmental ability of the oocytes. Vitrification and slow freezing both impair the rabbit oocytes viability after thawing but the processes act differently. Further studies are needed to improve the cryopreservation techniques in rabbit species. Moreover, we underlined that morphology and maintenance of the structural integrity of the oocytes are not suitable enough to assess the potential for further development of cryopreserved M_II oocytes. The assessment of ATP metabolism allows efficient evaluation of the viability of the frozen or vitrified oocytes. It should be used in addition to parthenogenesis to better assess the potential for further development.