bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disentangling associational effects: both resource density and resource frequency affect search behaviour in complex environments
Authors: Verschut Thomas A. , Becher Paul G. , Anderson Peter , Hambäck Peter A. 
Published: April 2016

Summary

Neighbouring resources have been found to either decrease or increase the likelihood that a consumer organism attacks a focal resource. These phenomena are referred to as associational resistance (AR) and associational susceptibility (AS), respectively. While associational effects have been observed in various field studies, little is known on how resource heterogeneity can cause associational effects.

We used a laboratory approach in which we studied the effects of resource density and frequency in the search behaviour of Drosophila melanogaster as a model organism for olfactory‐guided behaviour in insects. We first determined whether D. melanogaster could discriminate between odour sources that differ quantitatively. Secondly, we determined what the effect of resource density and frequency was on the search behaviour of D. melanogaster by combining these resources into various patch arrangements. Finally, we used the outcome of our experiments to disentangle the role of resource density and frequency in associational effects.

We found that D. melanogaster has the ability to discriminate between quantitatively different resources, but that the attraction to resource density is constrained by an optimum after which attraction decreases. Furthermore, in heterogeneous environments, flies showed a strong preference towards the more apparent resource, leading to AS for the more apparent resources and AR for the less apparent resource. The strength of this interaction increased with a decreasing frequency of the more apparent resource.

These results imply that D. melanogaster mainly selects patches at the level of individual resources. Consequently, when a patch contains qualitatively different resources, the more apparent resource will attract a higher number of flies than the less apparent resource irrespective of the frequency of the apparent resource within the patch.

Our study shows that associational effects can be explained by determining the hierarchical level at which a consumer selects its resources. When a consumer selects resources at the individual level rather than at the patch level, our results can be used to explain the population dynamics of host plants and their associated consumers under field conditions.

A lay summary is available for this article.
Beyond plant–soil feedbacks: mechanisms driving plant community shifts due to land‐use legacies in post‐agricultural forests
Authors: de la Peña Eduardo , Baeten Lander , Steel Hanne , Viaene Nicole , De Sutter Nancy , De Schrijver An , Verheyen Kris 
Published: April 2016

Summary

Although biotic legacies of past agricultural practices are widespread and increasing in contemporary ecosystems, our understanding of the mechanisms driving such legacies is still poor. Forest understories on former agricultural land show low frequencies and abundance of typical woodland species when compared with ancient forests.

These community shifts have been ascribed to the effects of dispersal limitation. A rarely considered mechanism is that post‐dispersal processes driven by plant‐associated communities determine the poor performance and recruitment of woodland indicators. Given the strong alterations in soil conditions due to former agricultural practices, we hypothesized that (abiotic) plant–soil feedbacks could be a major factor in community shifts.

We addressed this hypothesis by comparing plant‐associated communities in the soil and above the ground in ancient and post‐agricultural alluvial forests; then, we experimentally tested whether the changes in biotic and abiotic soil properties could affect above‐ground herbivore abundance and pressure and plant performance.

Ancient and post‐agricultural communities clearly differed in composition at different levels of the food web. Besides the plant community, we also observed the differences in the microbial and nematode community with increased abundance of root‐feeding nematodes in post‐agricultural soils. The composition of the above‐ground invertebrate community did not differ in ancient and post‐agricultural forest parcels; however, plants growing in post‐agricultural sites showed higher abundance of invertebrate herbivores and suffered more herbivory. Nutrient analyses of soil and plants showed that increased levels of phosphorus (and to a lesser extent, nitrogen) made plants more nutritious for insect herbivores. Laboratory experiments further pointed to this mechanism as an explanation of the poorer performance of woodland indicators in post‐agricultural woodlands.

Our results point to biotic and abiotic plant–soil feedbacks coupled with herbivory as a new mechanism to explain the legacy effects in temperate forests. The modification of the below‐ground community and soil abiotic characteristics by previous agricultural activity affects not only the plant growth but also the plant nutrient content in the compared understorey species, making them more susceptible to above‐ground herbivory. Our results provide one of the first examples of integrating plant–soil feedback and above‐ and below‐ground interactions to explain land‐use legacies.
Dietary niche constriction when invaders meet natives: evidence from freshwater decapods
Authors: Jackson Michelle C. , Grey Jonathan , Miller Katie , Britton J. Robert , Donohue Ian 
Published: April 2016

Summary

Invasive species are a key driver of global environmental change, with frequently strong negative consequences for native biodiversity and ecosystem processes. Understanding competitive interactions between invaders and functionally similar native species provides an important benchmark for predicting the consequences of invasion. However, even though having a broad dietary niche is widely considered a key factor determining invasion success, little is known about the effects of competition with functionally similar native competitors on the dietary niche breadths of invasive species.

We used a combination of field experiments and field surveys to examine the impacts of competition with a functionally similar native crab species on the population densities, growth rates and diet of the globally widespread invasive red swamp crayfish in an African river ecosystem.

The presence of native crabs triggered significant dietary niche constriction within the invasive crayfish population. Further, growth rates of both species were reduced significantly, and by a similar extent, in the presence of one another. In spite of this, crayfish maintained positive growth rates in the presence of crabs, whereas crabs lost mass in the presence of crayfish. Consequently, over the 3‐year duration of the study, crab abundance declined at those sites invaded by the crayfish, becoming locally extinct at one.

The invasive crayfish had a dramatic effect on ecosystem structure and functioning, halving benthic invertebrate densities and increasing decomposition rates fourfold compared to the crabs. This indicates that replacement of native crabs by invasive crayfish likely alters the structure and functioning of African river ecosystems significantly.

This study provides a novel example of the constriction of the dietary niche of a successful invasive population in the presence of competition from a functionally similar native species. This finding highlights the importance of considering both environmental and ecological contexts in order to predict and manage the impacts of invasive species on ecosystems.
Good reasons to leave home: proximate dispersal cues in a social spider
Authors: Berger‐Tal Reut , Berner‐Aharon Na'ama , Aharon Shlomi , Tuni Cristina , Lubin Yael 
Published: April 2016

SummaryNatal dispersal is a successful tactic under a range of conditions in spite of significant costs. Habitat quality is a frequent proximate cause of dispersal, and studies have shown that dispersal increases both when natal habitat quality is good or poor. In social species kin competition, favouring dispersal may be balanced by the benefits of group living, favouring philopatry.We investigated the effect of changes in the local environment on natal dispersal of adult females in a social spider species,Stegodyphus dumicola(Araneae, Eresidae), with a flexible breeding system, where females can breed either within the colony or individually following dispersal.We manipulated foraging opportunities in colonies by either removing the capture webs or by adding prey and recorded the number of dispersing females around each focal colony, and their survival and reproductive success. We predicted that increasing kin competition should increase dispersal of less‐competitive individuals, while reducing competition could cause either less dispersal (less competition) or more dispersal (a cue indicating better chances to establish a new colony).Dispersal occurred earlier and at a higher rate in both food‐augmented and web‐removal colonies than in control colonies. Fewer dispersing females survived and reproduced in the web‐removal group than in the control or food‐augmented groups.The results support our prediction that worsening conditions in web‐removal colonies favour dispersal, whereby increased kin competition and increased energy expenditure on web renewal cause females to leave the natal colony. By contrast, prey augmentation may serve as a habitat‐quality cue; when the surrounding habitat is expected to be of high quality, females assess the potential benefit of establishing a new colony to be greater than the costs of dispersal.
A pilot study of the utility of choline PET–CT in prostate cancer biochemical relapse following radical prostatectomy
Authors: Tan Hendrick , Joseph David , Loh Nelson K , McCarthy Michael , Leong Eugene , Siew Teck , Segard Tatiana , Morandeau Laurence , Trevenen Michelle , Francis Roslyn J 
Published: April 2016

AbstractIntroductionTo evaluate the detection rate of positive choline PET–CT and its clinical role in assisting with management decisions and the correlation between positive choline PET–CT and clinical/pathological parameters in prostate cancer patients with biochemical relapse following radical prostatectomy.MethodsThis was a longitudinal observational pilot study of 34 patients who received choline PET–CT scans with biochemical relapse after radical prostatectomy. Variables including peak PSA, PSA doubling time (DT), Gleason score, age, initial PSA at diagnosis, use of ADT prior to PET and initial clinical staging were statistically analysed to assess for independent predictive factors for positive PET findings.ResultsCholine PET–CT was positive in 38.2% of patients (13/34). The only statistically significant predictor for positive PET–CT was the use of ADT prior to PET–CT, with OR 18.7 (95% CI, 2.87–122.45), P < 0.01. Mean peak PSA for patients with positive PET–CT was 5.5 ± 4.8 ng/mL. Patients with positive PET–CT had a mean PSA DT of 5.1 ± 3.8 months and mean total Gleason of 7.6 ± 0.8. Although these variables were not statistically significant, they showed a tendency towards significance. At Receiver Operator Characteristics (ROC) analysis, a peak PSA value of 1.65 ng/mL and PSA DT of 4.4 months were determined to be the optimal cut‐off values predicting positive PET–CT.ConclusionCholine PET–CT has its potential as a diagnostic modality enabling the detection of occult prostate cancer recurrence and to differentiate localised disease from systemic disease thus guiding management. Use of ADT prior to PET–CT is a significant predictor of positive PET–CT. Patients with a short PSA DT, high‐peak PSA and high Gleason score should also be considered for choline PET–CT.
Evolution and adaptation of SAR11 and Cyanobium in a saline Tibetan lake
Authors: Oh Seungdae , Zhang Rui , Wu Qinglong L. , Liu Wen‐Tso 
Published: April 2016

SummaryLake Qinghai is a unique lacustrine ecosystem located on the Tibetan Plateau and exhibits oligotrophic, alkaline, and saline conditions. Previous studies have focused on the community phylogenetic diversity of bacterioplankton in the ecosystem. This study aimed to address the ecotype diversity of bacterioplankton populations in the unique microbial habitat, using metagenomic sequencing and analysis. Phylogenetic analysis revealed two major bacterial populations: SAR11 IIIa (14% of the total) and Cyanobium (14%). Although the two populations shared high 16S rRNA gene sequence identity (> 98% identity) with their closest marine counterparts, they displayed substantial genomic divergence (≤ 80% average amino acid sequence identity). Comparative genomic analysis identified conservation of carbon and energy storage metabolism (biosynthesis of polyphosphate and polyhydroxyalkanoate) gene operons in the SAR11 IIIa and a cyanate (potential nitrogen source in alkaline conditions) transporter gene operon in the Cyanobium. We further identified genetic signature of positive selection acting on an exodeoxyribonuclease gene of the SAR11 IIIa population, which is potentially associated with DNA repair responsive to strong UV radiation on the high altitude mountain. Taken together, our results revealed the ecosystem‐specific gene content of the bacterioplankton populations and provided new insights into their adaptations unique to the Tibetan lake.
Variability in progeny production and virulence of cyanophages determined at the single‐cell level
Authors: Kirzner Shay , Barak Efrat , Lindell Debbie 
Published: April 2016

SummaryLittle information regarding viral progeny production (burst size) and host mortality (viral virulence) is currently available for environmentally relevant phages. This is partially due to the difficulty in accurately measuring these infection properties with existing methods. Here, we set up a simple system for determining viral virulence and burst size at the single‐cell level following flow cytometric separation of infected cells. We applied this assay to two distinct cyanomyoviruses, Syn9 and S‐TIM5, during infection of two marine Synechococcus strains each. We found that virulence ranged from 44%–82%, differing for the same phage on different hosts. Average burst sizes ranged from 21–43 infective viruses/cell, and differed with host for Syn9, whereas the burst size of S‐TIM5 was similar for both hosts. In addition, virulence and burst sizes were different for the two phages when infecting their common host. Furthermore, wide‐ranging cell‐to‐cell variability was found for single‐cell burst sizes in each of the four interactions, ranging from 2 to over 100 infective viruses/cell. This variability, discerned at both the population and single‐cell levels under controlled laboratory conditions, is likely to be much more complex in natural environments.
Varroa destructor and viruses association in honey bee colonies under different climatic conditions
Authors: Giacobino Agostina , Molineri Ana I. , Pacini Adriana , Fondevila Norberto , Pietronave Hernán , Rodríguez Graciela , Palacio Alejandra , Bulacio Cagnolo Natalia , Orellano Emanuel , Salto César E. , Signorini Marcelo L. , Merke Julieta 
Published: April 2016

SummaryHoney bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybee‐pathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non‐treated colonies that did not received any treatment for the last 4 years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on deformed wing virus (DWV) amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non‐treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and virus presence.
Mucosa‐attached bacterial community in Crohn's disease coheres with the clinical disease activity index
Authors: Schäffler Holger , Herlemann Daniel P. R. , Alberts Christian , Kaschitzki Annika , Bodammer Peggy , Bannert Karen , Köller Thomas , Warnke Philipp , Kreikemeyer Bernd , Lamprecht Georg 
Published: April 2016

SummaryIn inflammatory bowel diseases (IBD), microbial communities often become imbalanced suggesting abnormal microbial‐gut interactions. In this study, we analysed the mucosa‐attached gut microbiota from 26 Crohn's disease (CD) patients using 16S rRNA gene amplicon sequencing. The samples were stratified according to their disease activity (Crohn's disease activity index, CDAI). The different disease activity categories had a comparable bacterial richness. Bacterial communities of patients in remission and intermediate CDAI (0–220) were relatively similar and dominated by the genus Bacteroides (>40%). The bacterial composition of patients assigned to a high CDAI category was dominated by Pelomonas (25%) and Flavobacterium (13%) but had a low relative abundance of Bacteroidetes (4%). This indicates the presence of specific abundant bacterial taxa at different CDAI levels. In addition, bacterial communities were also significantly influenced when a tumour necrosis factor (TNF)‐α inhibitor was applied or by the local mucosal inflammation level. As a consequence, a shift of the microbial composition may also indicate a change of the disease activity in CD patients.
Listeria monocytogenes remodels the cell surface in the blood‐stage
Authors: Quereda Juan J. , García‐del Portillo Francisco , Pucciarelli M. Graciela 
Published: April 2016

SummaryAfter crossing the intestinal barrier, the bacterial pathogen Listeria monocytogenes disseminates via the blood to the liver, spleen, brain and placenta. Transcriptomic studies have shown that L. monocytogenes changes expression of many genes during this blood‐stage. However, no comparable data at the protein level are known. As main interactors with the environment, we focused in surface proteins produced by L. monocytogenes in an ex vivo bovine blood model. Bacteria exposed to blood alter selectively the amount of several surface proteins compared with bacteria grown in laboratory media. Increased levels were detected for Lmo0514 and Internalin A, two surface proteins covalently bound to peptidoglycan, and the moonlighting protein alcohol‐acetaldehyde dehydrogenase, also known as Lap for ‘Listeria adhesion protein’. Lmo0514, induced by L. monocytogenes inside epithelial cells, is required for survival in plasma and for virulence in mice at early infection stages. Lmo0514 is also important to cope with low pH stress. By contrast, L. monocytogenes down‐regulates other surface proteins following exposure to blood and plasma such as Internalin I. These data provide evidence for remodelling of the L. monocytogenes cell surface during the blood‐stage, which it could facilitate pathogen dissemination to deep organs.
The association between meal timing and frequency with cardiometabolic profile in patients with bipolar disorder
Authors: Soreca I. , Wallace M. L. , Hall M. H. , Hasler B. P. , Frank E. , Kupfer D. J. 
Published: April 2016

ObjectiveThe goal of this study was to explore the association of timing of and frequency of meals with markers of cardiometabolic risk in patients with bipolar disorder in out‐patient maintenance treatment.MethodsWe used Pittsburgh Sleep Diary and actigraphy measures for individuals with bipolar I disorder. Linear and logistic regression analyses were used to determine whether dinnertime, instability of dinnertime, and/or interval between meals were associated with metabolic syndrome and its components.ResultsLater dinnertime was associated with greater waist circumference (β = 0.25, P = 0.02) after adjusting for age, sex, dinner‐to‐bed interval, and sleep duration. Longer breakfast‐to‐lunch intervals were also associated with greater waist circumferences (β =−.35, P = .002) after adjusting for age, sex, and sleep duration. Neither instability of dinnertime nor number of meals per day was associated with the metabolic syndrome or its components.ConclusionWeight gain is often perceived as inevitable side‐effect of medications. While patients often need to be on medication to function, a more careful lifestyle assessment with attention to social rhythms and timing of activities may be critical not only for mood stability, but also to reduce cardiovascular risk.
Ant megadiversity and its origins in arid Australia
Authors: Andersen Alan N 
Published: April 2016

AbstractIt is widely recognised that arid Australia (including semi‐ and seasonally arid regions) supports an extremely diverse ant fauna. However, the truly remarkable extent of its diversity is not well appreciated, even among myrmecologists, and the reasons for such diversity are poorly understood. The vast majority of ant species in arid Australia are undescribed, and I argue that a recognition of the true diversity of the fauna would re‐define the conventional understanding of global ant diversity patterns. For example,MonomoriumMayr andTetramoriumMayr are formally recognised as widespread but essentially Afrotropical genera, whereas the large majority of species actually occur in arid Australia. The Australian fauna includes many genera each with >100 arid‐adapted species, and several of these have >300 species.MelophorusLubbock is likely to have well over 1000 species, making it one of the world's richest ant genera despite being endemic to Australia. I estimate that the total size of the ant fauna of arid Australia is as much as 7500 species, which would make it rival, if not surpass, that of the Amazon basin. I argue that the phenomenal ant diversity of arid Australia is a product of its unique history of aridity and associated patterns of speciation and extinction over the past few million years. I propose that the Pleistocene glaciations that caused waves of mass extinctions throughout the northern hemisphere actually promoted speciation in Australia. Australia remained relatively warm during glacial periods, but there was massive movement of sand during these times of peak aridity, with up to 85% of the continent covered by desert dunes. This would have resulted in a highly fragmented biota confined to a very large number of isolated refugia, providing the perfect storm for speciation.