bluuebunny/crossref_metadata_2025_split huggingface dataset:
Winter warming events damage sub‐Arctic vegetation: consistent evidence from an experimental manipulation and a natural event
Authors: Bokhorst Stef F. , Bjerke Jarle W. , Tømmervik Hans , Callaghan Terry V. , Phoenix Gareth K. 
Published: August 2009

Summary 1.  The Arctic is experiencing considerable change in climate, particularly in winter, and a greater frequency of extreme climatic events is expected. However, the impacts of winter climate change and extreme events have received far less attention than the impacts of season‐long summer warming. Here we report findings from observations following a natural event and from experimental studies to show that short (<10 days) extreme winter warming events can cause major damage to sub‐Arctic plant communities at landscape scales. 2.  In the landscape observations, impacts were assessed following an extreme winter warming event that occurred in December 2007 in northern Scandinavia. During this event, temperatures rose up to 7 °C resulting in loss of snow cover and exposure of vegetation to firstly warm and then returning cold temperatures. 3.
In the following summer, extensive areas of damaged dwarf shrub vegetation could be observed. Ground observations showed damaged areas to have a 16 times greater frequency of dead shoots of the dominant shrub Empetrum hermaphroditum, resulting in 87% less summer growth compared to neighbouring undamaged areas. The landscape scale extent of this damage was confirmed by satellite‐derived Normalized Differential Vegetation Index values that showed a considerable 26% reduction (comparing July 2007 with July 2008 values) over an area of 1424 km2. This reduction indicates a significant decline in either leaf area or photosynthetic capacity or efficiency at the landscape scale. 4.
Strikingly similar damage was also observed in a field manipulation experiment using heating lamps and soil warming cables to simulate such extreme events in sub‐Arctic heathland over two winters. Here, an up to 21 times greater frequency of dead shoots and 47% less shoot growth of E. hermaphroditum was observed in plots exposed to simulated winter warming events compared to unmanipulated controls. 5.
Synthesis. These combined landscape observations and experimental findings provide compelling evidence that winter warming events can cause considerable damage to sub‐Arctic vegetation. With increasing winter temperatures predicted, any increase in such damage may have major consequences for productivity and diversity of these sub‐Arctic ecosystems, in contrast to the greening of parts of the Arctic currently attributed to summer warming.
Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesis
Authors: Smit Christian , Rietkerk Max , Wassen Martin J. 
Published: August 2009

Summary 1.  The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and strength of species interactions change along stress gradients, and to calls for new empirical and theoretical work. 2.  In the latest attempt in this journal, it is successfully argued how the SGH should be expanded by considering different life strategies of species (stress tolerance versus competitive ability) and characteristics of abiotic stress (resource versus non‐resource based) over wider stress gradients (opposed to low–high contrasts), but the crucial role of biotic stress by consumers is largely ignored in this refinement. 3.  We point out that consumers strongly alter the outcome of species interactions in benign and harsh environments, and show how inclusion of consumer‐incurred biotic stress alters the predicted outcome of interactions along resource‐ and non‐resource‐based stress gradients for stress‐tolerant and competitive benefactors and beneficiaries. 4.
Synthesis. New studies should include stress gradients consisting of both abiotic and biotic components to disentangle their impacts, and to improve our understanding of how species interactions change along environmental gradients.
A mutational wrench in the HAMP gearbox
Authors: Manson Michael D. 
Published: August 2009

SummaryHAMP domains communicate between input and output signalling elements in bacterial proteins. In the Tsr chemoreceptor, they convert axial movement of transmembrane helix 2 into changes in packing of the cytoplasmic kinase‐control module (KCM). Zhou et al. suggest transmembrane helix 2 ‘tugs’ on HAMP to destabilize x‐da packing of the parallel four‐helix bundle of the HAMP homodimer. Attractants would inhibit tugging. HAMP stability may be inversely related to stability of the a‐d packing of the anti‐parallel four‐helix bundle of KCM, a relationship possibly facilitated by HAMP/KCM helical mismatch. The beauty of this idea lies in its simplicity and testability.
Seed viability determination in parasitic broomrapes (Orobanche and Phelipanche) using fluorescein diacetate staining
Authors: THOROGOOD C J , RUMSEY F J , HISCOCK S J 
Published: August 2009

SummaryFluorescein diacetate (FDA) was investigated as a potential viability stain for seeds of holoparasitic broomrapes Orobanche and Phelipanche (Orobanchaceae), using four weedy and two non‐weedy taxa. FDA viabilities were compared with the currently used 2,3,5‐triphenyl tetrazolium chloride (TTC) test, and in vitro germination induced by the strigolactone analogue GR‐24. Viable FDA‐stained seeds were characterised by bright yellow–green fluorescence under 450–490 nm blue light. These viable seeds could be discriminated from non‐viable seeds, in which low levels of fluorescence, similar to non‐stained control seeds were observed. FDA viabilities were not significantly different from those obtained using the TTC stain; however, viability values for both stains were consistently higher than levels of artificially induced germination. Positive TTC‐staining showed continuous variation that was difficult to interpret. Nevertheless, the TTC test does not involve grinding seeds, and therefore probably remains a practical alternative to FDA for screening soil samples contaminated with Orobanche and Phelipanche seeds, which indicates different applications for the two viability tests. Interestingly, the strigolactone analogue GR‐24 only induced germination in O. crenata, P. ramosa and O. minor, suggesting a high specificity towards this germination inducer among the species investigated. We suggest that FDA‐staining provides a potential alternative to the currently used TTC test for seed viability assays for Orobanche and Phelipanche, and other parasitic weeds which are an obstacle to crop cultivation.
An amino acid substitution at position 205 of acetohydroxyacid synthase reduces fitness under optimal light in resistant populations of Solanum ptychanthum
Authors: ASHIGH J , TARDIF F J 
Published: August 2009

SummaryThe Ala205Val substitution in acetohydroxyacid synthase confers herbicide resistance in Solanum ptychanthum, but the effect on fitness is unknown. This study aimed to compare the germination, growth, seed production and competitiveness of resistant (R) and susceptible (S) populations under various light conditions in the field and in a controlled environment. Under optimal light conditions of high irradiance and high red/far‐red, the S populations produced more seeds compared with R populations, despite no difference in germination and above‐ground vegetative productivity. Any reduction in light intensity and red/far‐red diminished the reproductive ability of both R and S populations. This effect was more pronounced for S, so that, under sub‐optimal conditions, there were no differences between the two types. Replacement series with three ratios of R:S (16:0, 8:8 and 0:16) showed no competitive difference between the two types. Under optimal light conditions, the S populations always had a higher reproductive output and fitness than the R populations. This would likely cause S individuals to dominate in the absence of herbicide selection pressure, if light competition is reduced.
Weed suppression ability of three winter wheat varieties at different row spacing under organic farming conditions
Authors: DREWS S , NEUHOFF D , KÖPKE U 
Published: August 2009

SummaryFor three seasons, six field trials were conducted in winter wheat (Triticum aestivum) at different sites in North Rhine‐Westphalia, Germany. The aim was to evaluate the performance of three varieties, which differ in their shading behaviour, in suppressing weeds under organic farming (Ökologischer Landbau) conditions and grown at three row spacings. The experimental factors were cultivar, row width and row orientation. Key parameters of crop and weed development, including ground cover and biomass, were assessed at different growth stages and analysed with anova. Growth of the site‐specific weed vegetation was significantly affected in five of six trials. Weed growth was reduced by cvs Astron and Pegassos compared with cv. Greif, and was lower at 12 cm compared with 24 cm row spacing. No effect of row orientation (East‐West, North‐South) on weed growth was observed. The more competitive cultivars Astron and Pegassos were taller than the less competitive cv. Greif and had higher ground cover and light interception, presumably induced by planophile leaf inclination and partly, in the case of cv. Astron, because of higher leaf area index (LAI). Narrow row spacing (12 cm), resulting in a more even spatial plant distribution, increased crop ground cover, LAI, dry matter and light interception. In two trials, the variety with planophile leaf inclination performed better at wider row spacing, suggesting that planophile wheat cultivars may be advantageous in wider row stands.
Relative fitness of females and hermaphrodites in a natural gynodioecious population of wild radish,Raphanus sativusL. (Brassicaceae): comparison based on molecular genotyping
Authors: MIYAKE K. , MIYAKE T. , TERACHI T. , YAHARA T. 
Published: August 2009

AbstractIn many gynodioecious species, sex determination involves both cytoplasmic male‐sterility (CMS) genes and nuclear genes that restore male function. Differences in fitness among genotypes affect the dynamics of those genes, and thus that of gynodioecy. We used a molecular marker to discriminate between hermaphrodites with and without a CMS gene in gynodioeciousRaphanus sativus.We compared fitness through female function among the three genotypes: females, hermaphrodites with the CMS gene and those without it. Although there was no significant difference among the genotypes in seed size, hermaphrodites without the CMS gene produced significantly more seeds, and seeds with a higher germination rate than the other genotypes, suggesting no fitness advantage for females and no benefit to bearing the CMS gene. Despite the lack of fitness advantage for females in the parameter values we estimated, a theoretical model of gynodioecy shows it can be maintained if restorer genes impose a cost paid in pollen production. In addition, we found that females invest more resources into female reproduction than hermaphrodites when they become larger. If environmental conditions enable females to grow larger this would facilitate the dynamics of CMS genes.
Complete lack of mitochondrial divergence between two species of NE Atlantic marine intertidal gastropods
Authors: KEMPPAINEN P. , PANOVA M. , HOLLANDER J. , JOHANNESSON K. 
Published: August 2009

AbstractSome mitochondrial introgression is common between closely related species, but distinct species rarely show substantial introgression in their entire distribution range. In this study, however, we report a complete lack of mitochondrial divergence between two sympatric species of flat periwinkles (Littorina fabalis and Littorina obtusata) which, based on previous allozyme studies, diverged approximately 1 Ma. We re‐examined their species status using both morphology (morphometric analysis) and neutral genetic markers (microsatellites) and our results confirmed that these species are well separated. Despite this, the two species shared all common cytochrome‐b haplotypes throughout their NE Atlantic distribution and no deep split between typical L. fabalis and L. obtusata haplotypes could be found. We suggest that incomplete lineage sorting explains most of the lack of mitochondrial divergence between these species. However, coalescent‐based analyses and the sympatric sharing of unique haplotypes suggest that introgressive hybridization also has occurred.
Selection of low investment in sex in a cyclically parthenogenetic rotifer
Authors: CARMONA M. J. , DIMAS‐FLORES N. , GARCÍA‐ROGER E. M. , SERRA M. 
Published: August 2009

AbstractCyclical parthenogens, which combine asexual and sexual reproduction, are good models for research into the ecological and population processes affecting the evolutionary maintenance of sex. Sex in cyclically parthenogenetic rotifers is necessary for diapausing egg production, which is essential to survive adverse conditions between planktonic growing seasons. However, within a planktonic season sexual reproduction prevents clonal proliferation. Hence, clones with a low propensity for sex should be selected, becoming dominant in the population as the growing season progresses. In this context, we studied the dynamics of the heritable variation in propensity for sexual reproduction among clones of aBrachionus plicatilisrotifer population in a temporary Mediterranean pond during the period the species occurred in plankton. Clonal isolates displayed high heritable variation in their propensity for sex. Moreover, the frequency of clones with low propensity for sex increased during the growing season, which supports the hypothesized short‐term selection for low investment in sex within a growing season. These results demonstrate (1) the inherent instability of the cyclical parthenogenetic life cycle, (2) the cost of sexual reproduction in cyclical parthenogens where sex produces diapausing eggs and (3) the role of the association between sexual reproduction and diapause in maintaining sex in these cyclical parthenogens.
Extra‐pair fertilizations contribute to selection on secondary male ornamentation in a socially monogamous passerine
Authors: ALBRECHT T. , VINKLER M. , SCHNITZER J. , POLÁKOVÁ R. , MUNCLINGER P. , BRYJA J. 
Published: August 2009

AbstractDespite considerable research effort, it remains unclear whether extra‐pair fertilizations (EPF) drive the evolution of male secondary ornamentation in socially monogamous systems. In this study, we test the hypothesis that EPF contribute to the evolution or maintenance of male feather ornamentation in a sexually dichromatic passerine, the Scarlet Rosefinch, Carpodacus erythrinus. We show that the colouration of ornamental breast feathers is a good predictor of basic sources of variation in male annual reproductive output in rosefinches and that the annual realized reproductive success of males is positively associated with measures of ornamental colouration only when gains and losses because of EPF are considered. The results indicate that EPF in rosefinches may rely on absolute (good genes) rather than self referential (genetic complementarity) criteria of mate choice. Our study corroborates the potentially important role of EPF in the evolution and/or maintenance of elaborate male ornaments in socially monogamous taxa.
Comparative analyses of actinobacterial genomic fragments from Lake Kinneret
Authors: Philosof Alon , Sabehi Gazalah , Béjà Oded 
Published: August 2009

SummaryThe high genomic G+C group of Actinobacteria possesses a variety of physiological and metabolic properties, and exhibits diverse lifestyles and ecological distribution. In recent years, Actinobacteria have been found to frequently dominate samples obtained from freshwater samples. Furthermore, phylogenetic analyses have shown that 16S rRNA genes from uncultured actinobacterial freshwater samples cluster in four distinct lineages. While these lineages are abundant, little is known about them and currently no pure‐culture representatives or genomic fragments of them are available. In a screen of a genomic library from the moderately eutrophic freshwater Lake Kinneret, five fosmid clones containing actinobacterial genomic fragments were found. Three ∼40 kb genomic fragments were chosen for sequencing. Fosmids K003 and K005 showed high similarity and were affiliated with the acIV actinobacterial freshwater lineage. Fosmid K004 was affiliated with the highly abundant acI lineage. A comparative genomic analysis revealed high synteny between the two freshwater clones K003 and K005 but a lower synteny between these two and the K004 fosmid. Fosmids K003 and K005 share an identical arrangement of arginine biosynthesis gene while K004 showed a slightly different arrangement by lacking the argF gene. Fosmid Ant4E12, an Antarctic actinobacterial clone, showed a higher synteny with K003/5 than K004 and a similar arginine operon, but in a different genomic context. The Clusters of Orthologous Groups categories assignment of the three fosmids yielded genes that were mostly involved in amino acid and nucleotide metabolism, as well as transport and ribosomal RNA translation, structure and biogenesis. These genomic fragments represent the first sequences to be published from these lineages, providing a cornerstone for future work on this environmentally dominant group.
Comparative analysis of the widespread and conserved PB1‐like viruses infecting Pseudomonas aeruginosa
Authors: Ceyssens Pieter‐Jan , Miroshnikov Konstantin , Mattheus Wesley , Krylov Victor , Robben Johan , Noben Jean‐Paul , Vanderschraeghe Simon , Sykilinda Nina , Kropinski Andrew M. , Volckaert Guido , Mesyanzhinov Vadim , Lavigne Rob 
Published: August 2009

SummaryWe examined the genetic diversity of lytic Pseudomonas aeruginosa bacteriophage PB1 and four closely related phages (LBL3, LMA2, 14‐1 and SN) isolated throughout Europe. They all encapsulate linear, non‐permuted genomes between 64 427 and 66 530 bp within a solid, acid‐resistant isometric capsid (diameter: 74 nm) and carry non‐flexible, contractile tails of approximately 140 nm. The genomes are organized into at least seven transcriptional blocks, alternating on both strands, and encode between 88 (LBL3) and 95 (LMA2) proteins. Their virion particles are composed of at least 22 different proteins, which were identified using mass spectrometry. Post‐translational modifications were suggested for two proteins, and a frameshift hotspot was identified within ORF42, encoding a structural protein. Despite large temporal and spatial separations between phage isolations, very high sequence similarity and limited horizontal gene transfer were found between the individual viruses. These PB1‐like viruses constitute a new genus of environmentally very widespread phages within the Myoviridae.
DNA content in the diagnostic biopsy for benign‐adjacent and cancer‐tissue areas predicts the need for treatment in men with T1c prostate cancer undergoing surveillance in an expectant management programme
Authors: Isharwal Sumit , Makarov Danil V. , Carter H. Ballentine , Epstein Jonathan I. , Partin Alan W. , Landis Patricia , Marlow Cameron , Veltri Robert W. 
Published: August 2009

Study Type – Prognosis (case series)Level of Evidence 4OBJECTIVETo assess the DNA content in benign‐adjacent and cancer‐tissue areas of a diagnostic biopsy, to predict which patients would subsequently develop an unfavourable biopsy necessitating treatment for prostate cancer in the expectant management (EM) programme.PATIENTS AND METHODSOf 71 patients who had benign‐adjacent and cancer‐tissue areas of diagnostic biopsies available, 39 developed unfavourable biopsies (Gleason score ≥7, Gleason pattern 4/5, three or more cores positive for cancer, >50% of any core involved with cancer), while 32 maintained favourable biopsies on annual surveillance examination (median follow‐up 3.7 years). DNA content was measured on Feulgen‐stained biopsy sections using an automatic imaging system (AutoCyteTM, TriPath Imaging Inc, Burlington, NC, USA). Cox proportional‐hazard regression and Kaplan‐Meier plots were used to identify significant predictors for unfavourable biopsy conversion.RESULTSUnivariately, DNA content measurements i.e. an excess of optical density (OD) in the benign‐adjacent tissuer area, and the sd of the OD in the cancer tissue were significant, with a hazard ratio and 95% confidence interval of 2.58 (1.17–5.68; P = 0.019) and 5.36 (1.89–15.24; P = 0.002), respectively, for predicting unfavourable biopsy conversion that required intervention. Also, several other DNA content measurements in benign‐adjacent and cancer‐tissue areas showed a trend to statistical significance. Further, benign‐adjacent excess of OD (3.12, 1.4–6.95; P = 0.005) and cancer sd of OD (5.88, 2.06–16.82; P = 0.001) remained significant in the multivariate model to predict unfavourable biopsy conversion. Patients with benign‐adjacent excess of OD > 25.0 and cancer sd of OD of >4.0 had the highest risk for unfavourable biopsy conversion (P < 0.001).CONCLUSIONSDNA content measurements in the benign‐adjacent and cancer‐tissue areas appear to be useful for predicting unfavourable biopsy conversion (a recommendation for intervention) on annual surveillance examinations in the EM programme.
Something old, something new: a developmental transition from familiarity to novelty preferences with hidden objects
Authors: Shinskey Jeanne L. , Munakata Yuko 
Published: August 2009

AbstractNovelty seeking is viewed as adaptive, and novelty preferences in infancy predict cognitive performance into adulthood. Yet 7‐month‐olds prefer familiar stimuli to novel ones when searching for hidden objects, in contrast to their strong novelty preferences with visible objects (Shinskey & Munakata, 2005). According to a graded representations perspective on object knowledge, infants gradually develop stronger object representations through experience, such that representations of familiar objects can be better maintained, supporting greater search than with novel objects. Object representations should strengthen with further development to allow older infants to shift from familiarity to novelty preferences with hidden objects. The current study tested this prediction by presenting 24 11‐month‐olds with novel and familiar objects that were sometimes visible and sometimes hidden. Unlike 7‐month‐olds, 11‐month‐olds showed novelty preferences with both visible and hidden objects. This developmental shift from familiarity to novelty preference with hidden objects parallels one that infants show months earlier with perceptible stimuli, but the two transitions may reflect different underlying mechanisms. The current findings suggest both change and continuity in the adaptive development of object representations and associated cognitive processes.