bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of facilitation on community stability and dynamics: synthesis and future directions
Authors: Butterfield Bradley J. 
Published: October 2009

Summary 1. New insights into the mechanisms and outcomes of facilitation have led to important advances in our understanding of ecological patterns and processes. However, the effects of facilitation on non‐successional community dynamics have yet to be developed into a general theory. 2. By synthesizing spatial and temporal relationships between biotic interactions and environmental severity, a new model of facilitation‐driven community dynamics is presented that applies to any facilitative mechanism related to abiotic stress or resource limitation. 3. In general, facilitation tends to stabilize community dynamics in moderately severe environments, due to a buffering effect of increased facilitation during more severe periods and enhanced competitive effects in milder conditions. In contrast, a strong negative relationship between environmental severity and facilitative strength in highly severe environments leads to a destabilizing effect of facilitation on community dynamics. 4. If only mature plants have significant facilitative effects, developmental lags may be introduced that decouple environmental fluctuations and community dynamics, decreasing the effects of facilitation on community stability. Additionally, dual regulation of facilitation by environmental and demographic factors decouples abundance from climate and produces periodic local extinctions. In general, the interplay of facilitation and competition produce highly variable dynamics in moderate‐severity environments, whereas qualitatively similar results were found in high‐severity environments regardless of facilitative mechanism or model parameters. 5. Additional variation in community dynamics can be explained by the combination of effect and response functional traits of species within a community. The relative abundance and proportion of species within a community falling into one of four different effect and response categories provide an effective framework for predicting responses to climatic variation and biotic interactions. 6.
Synthesis. Facilitation either increases or decreases community stability in predictable ways as a function of empirically identifiable environmental gradients. Effects of developmental lags, complex controls of facilitative mechanisms and species’ functional traits explain additional variation in community dynamics that can be applied to a broad array of ecosystems in which facilitation occurs.
Parasitic plants as facilitators: more Dryad than Dracula?
Authors: Watson David M. 
Published: October 2009

SummaryDespite being components of most vegetation types, the community‐level effects of parasitic plants are often ignored. The few studies adopting a broader view have revealed that these plants mediate a series of direct and indirect competitive and facilitative effects on community structure and ecosystem processes.I summarize findings from the two best‐studied systems: a set of experimental and manipulative studies from northern Sweden and an integrated research programme in southern Australia, both focusing on the most abundant hemiparasite in the region –Bartsia alpina(Orobanchaceae; Lamiales) andAmyema miquelii(Loranthaceae; Santalales), respectively.Despite broad‐based differences between these regions, their vegetation types and biotic constituents, rates of litter‐fall, litter decomposition, nutrient return and plant growth all increased near the hemiparasites in both cases. This leads to changes in the abundance of other plants and the increased species richness and total biomass reflects an indirect form of facilitation.In addition to reallocation of nutrients from host tissues, some of the additional nutrients may be excreted by other organisms, such as visiting pollinators, seed dispersers, herbivores and members of below‐ground decomposer communities. Small‐scale heterogeneity in nutrient availability could provide a mechanistic process underlying the role of parasitic plants as keystone resources.Parasitic plants can be regarded as either malevolent predators (Dracula) or charitable benefactors(Robin Hood), but may be better described as Dryads (Greek deities associated with specific trees, which, in addition to being reliant on their host for their wellbeing, affect nearby trees and visiting animals, rendering the surrounding stand a sacred grove).Synthesis.The Dryad role may be applicable to a wide range of facilitators, whereby indirect interactions with other organisms affect both hosts and adjacent plants, augmenting direct plant–plant interactions. However, while consistent with both case studies and information from studies of other parasitic plants, this role may be most apparent in low productivity systems. Addition, removal and animal exclosure experiments are highlighted as useful approaches to quantify the community‐level influence of parasitic plants, in addition to dedicated work on the below‐ground influences of parasitic plants.
Do facilitative interactions increase species richness at the entire community level?
Authors: Cavieres Lohengrin A. , Badano Ernesto I. 
Published: October 2009

Summary 1. Although the consequences of facilitation at individual and population levels are well known, the community‐level consequences of these processes have received much less attention. In particular, the importance of facilitation in determining richness at the entire community level has seldom been evaluated. 2. In this study, we sampled 11 alpine plant communities along the southern Andes in South America, spanning from tropical (25°S) to sub‐antarctic latitudes (55°S). Plant communities were dominated by cushion plants, a particular growth form that acts as a nurse plant for other plant species. Through rarefaction curves, we assessed the effectiveness of community sampling and estimated the number of species present within and outside cushions. Non‐metric Multidimensional Scaling ordinations (NMDS) were used to assess differences between the species assemblages growing within and outside cushions. Finally, samples from cushions and open areas were combined in a single matrix accounting for the difference in cover between both microhabitats, and through rarefaction curves we assessed how many more species are added to the community due to the presence of cushions. 3. Samples taken within cushions always contained more species than equivalent samples from open areas. However, the magnitude of this difference varied among communities. NMDS ordination indicated that cushions generate species assemblages structurally different from those found in open areas. Inclusion of samples from cushion and open areas in synthetic analyses – where differences in cover were accounted for – indicated that the presence of cushions consistently increased species richness at the entire community level. The magnitude of these increases in species richness varied with habitat severity, with lower values at both extremes of the environmental severity gradient. 4.
Synthesis. Facilitative interactions with cushion nurse plants along the high Andes of southern South America changed plant assemblage structure and increased species richness at the entire community level, indicating that facilitative interactions are pivotal in maintaining the diversity of these harsh environments.
Unravelling the nature of postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: the role of elastase, complement C4a and interleukin‐1β
Authors: Nijs J. , Van Oosterwijck J. , Meeus M. , Lambrecht L. , Metzger K. , Frémont M. , Paul L. 
Published: October 2009

Abstract.  Nijs J, Van Oosterwijck J, Meeus M, Lambrecht L, Metzger K, Frémont M, Paul L (Vrije Universiteit Brussel, Brussels; University College Antwerp, Antwerp; University Hospital Brussels, Brussels; Private Practice for Internal Medicine, Gent/Aalst; and RED Laboratories N.V., Zellik; Belgium, and University of Glasgow, Glasgow, UK). Unravelling the nature of postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: the role of elastase, complement C4a and interleukin‐1β. J Intern Med 2010; 267: 418–435.Objectives.  Too vigorous exercise or activity increase frequently triggers postexertional malaise in people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a primary characteristic evident in up to 95% of people with ME/CFS. The present study aimed at examining whether two different types of exercise results in changes in health status, circulating elastase activity, interleukin (IL)‐1β and complement C4a levels.Design.  Comparative experimental design.Setting.  University.Subjects.  Twenty‐two women with ME/CFS and 22 healthy sedentary controls Interventions: participants were subjected to a submaximal exercise (day 8) and a self‐paced, physiologically limited exercise (day 16). Each bout of exercise was preceded and followed by blood sampling, actigraphy and assessment of their health status.Results.  Both submaximal exercise and self‐paced, physiologically limited exercise resulted in postexertional malaise in people with ME/CFS. However, neither exercise bout altered elastase activity, IL‐1β or complement C4a split product levels in people with ME/CFS or healthy sedentary control subjects (P > 0.05). Postexercise complement C4a level was identified as a clinically important biomarker for postexertional malaise in people with ME/CFS.Conclusions.  Submaximal exercise as well as self‐paced, physiologically limited exercise triggers postexertional malaise in people with ME/CFS, but neither types of exercise alter acute circulating levels of IL‐1β, complement C4a split product or elastase activity. Further studying of immune alterations in relation to postexertional malaise in people with ME/CFS using multiple measurement points postexercise is required.
Trends in preterm births in Flanders, Belgium, from 1991 to 2002
Authors: Keirse Marc J. N. C. , Hanssens Myriam , Devlieger Hugo 
Published: October 2009

SummaryChanges in the preterm birth rate have been attributed predominantly to increases in multiple pregnancies, associated with advanced maternal age and assisted reproduction, and to obstetric intervention. We examined their contribution to the frequencies of preterm (<37 weeks), very preterm (<32 weeks) and severely preterm (<28 weeks) birth among 700 383 singleton and twin births in Flanders from 1991 to 2002. We examined changes across four 3‐year periods (triennia) with confidence interval [CI] analysis and yearly incremental rates using linear and logistic regression analyses.Over the 12 years, twin pregnancies increased from 1.5% to 2.0%, averaging 1.6% [95% CI 1.54, 1.66] in 1991–93 and 1.9% [95% CI 1.81, 1.94] in 2000–02 (P < 0.001). The proportion of women aged 35 years or more increased from 6.8% [95% CI 6.69, 6.92] in 1991–93 to 11.3% [95% CI 11.2, 11.5] in 2000–02 (P < 0.001) and those aged under 20 from 1.9% [95% CI 1.81, 1.93] to 2.3% [95% CI 2.26, 2.41] (P < 0.001). Assisted reproduction increased from 2.6% [95% CI 2.48, 2.62] to 4.2% [95% CI 4.11, 4.30] (P < 0.001) and obstetric intervention to end pregnancy from 36.2% [95% CI 36.0, 36.4] to 40.3% [95% CI 40.1, 40.6] (P < 0.001). These increases related to an annual increase of 0.23% in the preterm birth rate from 5.5% [95% CI 5.4, 5.6] in 1991–93 to 7.2% [95% CI 7.1, 7.3] in 2000–02 (P < 0.001). The proportions of very and severely preterm births also increased by nearly a third, but their contribution to the total preterm birth rate remained stable at 15% and 5%, respectively. Odds ratios for the increases per year were 1.035 [95% CI 1.032, 1.038] for preterm birth, 1.024 [95% CI 1.018, 1.031] for very preterm and 1.028 [95% CI 1.017, 1.040] for severely preterm births after adjusting for other changes in the population.Overall, the data show, first, marked increases in the frequency of known contributors to the preterm birth rate, including twin pregnancies, advanced maternal age, assisted reproduction and obstetric intervention. Second, the preterm birth rate further increased significantly within subgroups of women with one or more of these characteristics. Third, the preterm birth rate also rose, from 4.4% [95% CI 4.2, 4.5] in 1991–93 to 5.6% [95% CI 5.5, 5.8] in 2000–02 (P < 0.001), in women with none of these contributing factors. This indicates that changes in the frequency of these known predictors are insufficient to explain the steady increase in preterm, very preterm and severely preterm births over more than a decade.
Association of allergic patients’ phenotypes with IgE reactivity to recombinant pollen marker allergens
Authors: Twardosz‐Kropfmüller A. , Singh M. B. , Niederberger V. , Horak F. , Kraft D. , Spitzauer S. , Valenta R. , Swoboda I. 
Published: October 2009

To cite this article: Twardosz‐Kropfmüller A, Singh MB, Niederberger V, Horak F, Kraft D, Spitzauer S, Valenta R, Swoboda I. Association of allergic patients’ phenotypes with IgE reactivity to recombinant pollen marker allergens. Allergy 2010; 65: 296–303.AbstractBackground:  During the last decade allergen molecules from several allergen sources have been produced by recombinant DNA technology. The aim of this study was to investigate whether IgE reactivity to recombinant pollen allergens with broad and narrow cross‐reactivity is associated with clinical phenotypes of allergic sensitization.Methods:  Serum IgE reactivity to a panel of six recombinant birch and grass pollen allergens was measured by ELISA in pollen sensitized patients from Central Europe to define groups of patients with exclusive IgE reactivity to rBet v 1, with exclusive reactivity to major grass pollen allergens (rPhl p 1, rPhl p 2, rPhl p 5) and with IgE reactivity to cross‐reactive pollen allergens (rBet v 2, rPhl p 7). Patients’ clinical phenotypes were recorded. IgE responses to tree, grass and weed pollen as well as plant food extracts were evaluated in vitro by CAP‐FEIA and clinical sensitivities were confirmed in vivo by skin prick testing.Results:  IgE reactivity to the recombinant major birch pollen allergen, rBet v 1, was associated with sensitization to pollen from birch, taxonomically related trees and to certain plant‐derived food. Reactivity to the recombinant timothy grass pollen allergens, rPhl p 1, rPhl p 2, rPhl p 5, indicated sensitization to pollen from grasses. Patients reacting with the highly cross‐reactive allergen rPhl p 7 were polysensitized to pollen from unrelated trees, grasses and weeds and rBet v 2‐positive patients were polysensitized to pollen and plant‐derived food from unrelated plants.Conclusions:  IgE reactivity to recombinant marker allergens is associated with clinical phenotypes of allergic sensitization and may be useful for the selection of treatment strategies.
Detection of herpetic viruses in gingival crevicular fluid of patients suffering from periodontal diseases: prevalence and effect of treatment
Authors: Grenier G. , Gagnon G. , Grenier D. 
Published: October 2009

Background/Aim:  Although the role of bacteria in the etiology of periodontitis is well established, it has been suggested that herpetic viruses could contribute to the initiation and progression of this disease. The aim of this study was to determine the prevalence of human cytomegalovirus (HCMV), Epstein–Barr virus (EBV) and herpes simplex virus (HSV) in gingival crevicular fluid (GCF) samples obtained from periodontally healthy, gingivitis and periodontitis patients. In addition, the effect of periodontal treatment (scaling and root planing) on the persistence of herpetic viruses was evaluated in a sub‐group of patients suffering from chronic periodontitis.Methods:  The presence of viruses in GCF samples was assessed by a nested PCR amplification technique. The persistence of viruses in periodontal sites was evaluated following a scaling and root planing therapy.Results:  A statistically significant higher prevalence of HCMV was observed in periodontitis patients as compared to healthy control subjects (35 vs. 8%, respectively; P = 0.0377). A trend for a higher prevalence of HSV was also noted in the periodontitis group, in comparison with healthy control subjects. In addition, a higher prevalence of HCMV was associated with deep periodontal pockets in subjects suffering from periodontitis. In the sub‐group of periodontitis patients, periodontal therapy resulted in the elimination (HCMV and EBV) or reduction (HSV) of the herpetic viruses.Conclusions:  This study showed that the prevalence of HCMV and HSV viruses in GCF is higher in patients suffering from periodontitis compared to periodontally healthy subjects, and that the prevalence of HCMV is higher in deep periodontal pockets. It also brought evidences that periodontal therapy may be associated with virus elimination in diseased sites.
Genetic diversity and toxic activity of Aggregatibacter actinomycetemcomitans isolates
Authors: Kawamoto D. , Ando E. S. , Longo P. L. , Nunes A. C. R. , Wikström M. , Mayer M. P. A. 
Published: October 2009

Introduction:  Very little is known of the diversity and expression of virulence factors of serotypes of Aggregatibacter actinomycetemcomitans. Toxic activity on Chinese hamster ovary (CHO) cells and cdt and ltx genotyping were evaluated in A. actinomycetemcomitans serotypes.Methods:  Forty‐one A. actinomycetemcomitans isolates were analysed for CHO cell growth inhibition. Genotyping was performed by polymerase chain reactions specific to the ltx promoter region, serotype‐specific and cdt region and by sequencing of cdtB.Results:  cdtABC was detected in 40 strains. Analysis of the cdtA upstream region revealed 10 cdt genotypes. Toxicity to CHO cells was detected for 92.7% of the isolates; however, no correlation between the toxic activity and the cdt genotype was detected. Serotype c was more prevalent among Brazilian samples (68.0%). Four serotype b isolates from subjects with aggressive periodontitis were associated with high leukotoxin production and exhibited moderate to strong toxic activity in CHO cells, but were classified in different cdt genotypes. High levels of toxicity in CHO cells were not associated with a particular serotype; 57.1% of serotype a isolates presented low toxicity to CHO cells whereas the highly toxic strains belonged to serotypes b and c. Sequencing of cdtB revealed a single nucleotide polymorphism of amino acid 281 but this was not related to the toxic activity in CHO cells.Conclusion:  Differences in prevalence of the low and highly cytotoxic strains among serotypes reinforce the hypothesis that serotype b and c isolates of A. actinomycetemcomitans are more virulent than serotype a strains.
Male Performance and Body Size Affect Female Re‐Mating Occurrence in the Orb‐Web Spider Leucauge mariana (Araneae, Tetragnathidae)
Authors: Aisenberg Anita 
Published: October 2009

AbstractFemales can affect male probabilities of paternity success through behavioural, morphological and/or physiological processes occurring during or after copulation. These processes under female‐control include the acceptance or rejection of mating attempts by subsequent males. Leucauge mariana is an orb weaving spider that shows male mate guarding of penultimate females, male–male competition on female webs and copulatory plugs, suggesting a polyandric mating system. The aim of the present study was to ascertain whether male behaviour during courtship and copulation in L. mariana relate with female re‐mating decisions. Forty‐three virgin females were exposed to up to three males until they mated. In 24 cases, the copulatory plug was absent after mating and females were exposed the next day to up to three other males. Eighteen females accepted a second mating. Relatively larger females were more receptive to second matings and were more likely to copulate if the second male was smaller. Longer duration of female tapping and abdominal bobbing during courtship, and first copulations with less short insertions and more flubs, were associated with increased female acceptance to second matings. The results indicate cryptic female choice on male courtship and copulatory performance and suggest female‐control over the determination of male mating success in this spider species.
On the competitiveness of Diabrotica virgifera virgifera damage abatement strategies in Hungary: a bio‐economic approach
Authors: Dillen K. , Mitchell P. D. , Tollens E. 
Published: October 2009

Abstract Diabrotica virgifera virgifera Le Conte or western corn rootworm (WCR) is a major pest of cultivated maize, Zea mays L., introduced into Europe in 1992. Since then, the beetle spread through Central Europe, leading to a continuous pest population in 11 European countries. This article presents an economic assessment of different damage abatement strategies against this invasive species in the Hungarian maize sector. A bio‐economic model, using Monte Carlo sampling, estimates the potential damage from WCR under no control and the value created by Bt maize, seed treatment, soil insecticides and cultural control. At the same time, potential market shares for the different damage abatement options under perfect information are deducted. The potential damages under a no control scenario are estimated at €176/ha for grain maize farmers on average, which points out the need for well‐designed damage abatement strategies. For land‐constrained farmers cultural control is a valuable damage abatement strategy, being the optimal choice in 69% of the cases. In monoculture Bt maize is the best option as it creates the highest value in 78% of the cases. However, as Bt maize active against WCR is not deregulated in the European Union, soil insecticides in 54% of the cases and seed treatment in 46% of the cases are the rational choices. As the value created by Bt maize is positive, not deregulating Bt maize in Hungary leads to benefits foregone ranging from €16/ha for land‐constrained grain farmers to €49/ha in the case of silage maize under monoculture. Finally, the results of the sensitivity analysis can be used to develop a multi‐criteria tool to aid farmers in applying the appropriate damage abatement strategy. This could decrease the dependency of farmers on scouting techniques and economic thresholds of WCR presence.
Saprophagous insect larvae,Drosophila melanogaster, profit from increased species richness in beneficial microbes
Authors: Rohlfs M. , Kürschner L. 
Published: October 2009

AbstractFemale fruit flies,Drosophila melanogaster, lay their eggs on decaying plant material. Foraging fly larvae strongly depend on the availability of dietary microbes, such as yeasts, to reach the adult stage. In contrast, strong interference competition with filamentous fungi can cause high mortality amongDrosophilalarvae. Given that many insects are known for employing beneficial microbes to combat antagonistic ones, we hypothesized that fly larvae engaged in competition with the noxious mouldAspergillus nidulansbenefit from the presence of dietary yeast species, especially when they are associated with increasingly species rich yeast communities (ranging from one to six yeast species per community). On a nutrient‐limited fruit substrate infested withA. nidulans, both larval survival and development time were positively affected by more diverse yeast communities. On a mould‐free fruit substrate, merely larval development but not survival was found to be affected by increasing species richness of dietary yeasts. Not only yeast diversity had an effect onD. melanogasterlife‐history traits, but also the identity of the yeast combinations. These findings demonstrate the importance of the structure and diversity of microbial communities in mutualistic animal–microbe interactions.