bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing the exposure of the built environment to potential ignition sources generated from vegetative fuel
Authors: Beverly J. L. , Bothwell P. , Conner J. C. R. , Herd E. P. K.
Published: May 2010

We assessed the exposure of the built environment to potential ignition sources generated from vegetative fuel for four communities in the province of Alberta, Canada. Ignition processes generated by burning vegetation that were included in the analysis were radiant heat, short-range spotting, and longer-range spotting. Results were used to map the boundaries of the wildland–urban interface and to delineate zones within each community that identify the degree to which these areas represent potential wildfire entry-points into the wildland–urban interface. The assessment method can be used to set priorities for mitigation activities; compare conditions within and between communities and over time; and identify priority areas for time- and resource-intensive site assessments that are often completed for individual structures located in the wildland–urban interface. We compared results among the four case-study communities and demonstrated an application of the approach for evaluating community fuel treatment plans. Factors that influenced the exposure of the built environment to potential ignition sources differed among the communities, which suggested the need for community-specific mitigation strategies. Spatial patterns of areas with elevated ignition exposure reflected not only the amount of ignition-producing vegetation around the built environment, but also the size and arrangement of fuel patches in relation to the unique morphology of the community and the occurrence of occluded interface zones.
Critique of Sikkink and Keane's comparison of surface fuel sampling techniques
Authors: Wright Clinton S. , Ottmar Roger D. , Vihnanek Robert E.
Published: May 2010

The 2008 paper of Sikkink and Keane compared several methods to estimate surface fuel loading in western Montana: two widely used inventory techniques (planar intersect and fixed-area plot) and three methods that employ photographs as visual guides (photoload, photoload macroplot and photo series). We feel, however, that their study design was inadequate to evaluate the accuracy of these methods when measured against a series of reference sites. Incorrect use may have contributed to the authors' inferences that the photo series method was the least accurate in this case. Furthermore, sampling efficiency was not adequately taken into account when evaluating overall efficacy of the five methods studied.
Mechanical tugging force regulates the size of cell–cell junctions
Authors: Liu Zhijun , Tan John L. , Cohen Daniel M. , Yang Michael T. , Sniadecki Nathan J. , Ruiz Sami Alom , Nelson Celeste M. , Chen Christopher S.
Published: May 2010

Actomyosin contractility affects cellular organization within tissues in part through the generation of mechanical forces at sites of cell–matrix and cell–cell contact. While increased mechanical loading at cell–matrix adhesions results in focal adhesion growth, whether forces drive changes in the size of cell–cell adhesions remains an open question. To investigate the responsiveness of adherens junctions (AJ) to force, we adapted a system of microfabricated force sensors to quantitatively report cell–cell tugging force and AJ size. We observed that AJ size was modulated by endothelial cell–cell tugging forces: AJs and tugging force grew or decayed with myosin activation or inhibition, respectively. Myosin-dependent regulation of AJs operated in concert with a Rac1, and this coordinated regulation was illustrated by showing that the effects of vascular permeability agents (S1P, thrombin) on junctional stability were reversed by changing the extent to which these agents coupled to the Rac and myosin-dependent pathways. Furthermore, direct application of mechanical tugging force, rather than myosin activity per se, was sufficient to trigger AJ growth. These findings demonstrate that the dynamic coordination of mechanical forces and cell–cell adhesive interactions likely is critical to the maintenance of multicellular integrity and highlight the need for new approaches to study tugging forces.
Ras signaling requires dynamic properties of Ets1 for phosphorylation-enhanced binding to coactivator CBP
Authors: Nelson Mary L. , Kang Hyun-Seo , Lee Gregory M. , Blaszczak Adam G. , Lau Desmond K. W. , McIntosh Lawrence P. , Graves Barbara J.
Published: May 2010

Ras/MAPK signaling is often aberrantly activated in human cancers. The downstream effectors are transcription factors, including those encoded by the ETS gene family. Using cell-based assays and biophysical measurements, we have determined the mechanism by which Ras/MAPK signaling affects the function of Ets1 via phosphorylation of Thr38 and Ser41. These ERK2 phosphoacceptors lie within the unstructured N-terminal region of Ets1, immediately adjacent to the PNT domain. NMR spectroscopic analyses demonstrated that the PNT domain is a four-helix bundle (H2–H5), resembling the SAM domain, appended with two additional helices (H0–H1). Phosphorylation shifted a conformational equilibrium, displacing the dynamic helix H0 from the core bundle. The affinity of Ets1 for the TAZ1 (or CH1) domain of the coactivator CBP was enhanced 34-fold by phosphorylation, and this binding was sensitive to ionic strength. NMR-monitored titration experiments mapped the interaction surfaces of the TAZ1 domain and Ets1, the latter encompassing both the phosphoacceptors and PNT domain. Charge complementarity of these surfaces indicate that electrostatic forces act in concert with a conformational equilibrium to mediate phosphorylation effects. We conclude that the dynamic helical elements of Ets1, appended to a conserved structural core, constitute a phospho-switch that directs Ras/MAPK signaling to downstream changes in gene expression. This detailed structural and mechanistic information will guide strategies for targeting ETS proteins in human disease.
Distinct Contributions of Conserved Modules to Runt Transcription Factor Activity
Authors: Walrad Pegine B. , Hang Saiyu , Joseph Genevieve S. , Salas Julia , Gergen J. Peter
Published: May 2010

Runx proteins play vital roles in regulating transcription in numerous developmental pathways throughout the animal kingdom. Two Runx protein hallmarks are the DNA-binding Runt domain and a C-terminal VWRPY motif that mediates interaction with TLE/Gro corepressor proteins. A phylogenetic analysis of Runt, the founding Runx family member, identifies four distinct regions C-terminal to the Runt domain that are conserved in Drosophila and other insects. We used a series of previously described ectopic expression assays to investigate the functions of these different conserved regions in regulating gene expression during embryogenesis and in controlling axonal projections in the developing eye. The results indicate each conserved region is required for a different subset of activities and identify distinct regions that participate in the transcriptional activation and repression of the segmentation gene sloppy-paired-1 (slp1). Interestingly, the C-terminal VWRPY-containing region is not required for repression but instead plays a role in slp1 activation. Genetic experiments indicating that Groucho (Gro) does not participate in slp1 regulation further suggest that Runt's conserved C-terminus interacts with other factors to promote transcriptional activation. These results provide a foundation for further studies on the molecular interactions that contribute to the context-dependent properties of Runx proteins as developmental regulators.
HOPS Initiates Vacuole Docking by Tethering Membranes before trans-SNARE Complex Assembly
Authors: Hickey Christopher M. , Wickner William
Published: May 2010

Vacuole homotypic fusion has been reconstituted with all purified components: vacuolar lipids, four soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, Sec17p, Sec18p, the Rab Ypt7p, and the hexameric homotypic fusion and vacuole protein sorting complex (HOPS). HOPS is a Rab-effector with direct affinity for SNAREs (presumably via its Sec1-Munc18 homologous subunit Vps33p) and for certain vacuolar lipids. Each of these pure vacuolar proteins was required for optimal proteoliposome clustering, raising the question of which was most directly involved. We now present model subreactions of clustering and fusion that reveal that HOPS is the direct agent of tethering. The Rab and vacuole lipids contribute to tethering by supporting the membrane association of HOPS. HOPS indirectly facilitates trans-SNARE complex formation by tethering membranes, because the synthetic liposome tethering factor polyethylene glycol can also stimulate trans-SNARE complex formation and fusion. SNAREs further stabilize the associations of HOPS-tethered membranes. HOPS then protects newly formed trans-SNARE complexes from disassembly by Sec17p/Sec18p.
A Nucleus-based Quality Control Mechanism for Cytosolic Proteins
Authors: Prasad Rupali , Kawaguchi Shinichi , Ng Davis T.W.
Published: May 2010

Intracellular quality control systems monitor protein conformational states. Irreversibly misfolded proteins are cleared through specialized degradation pathways. Their importance is underscored by numerous pathologies caused by aberrant proteins. In the cytosol, where most proteins are synthesized, quality control remains poorly understood. Stress-inducible chaperones and the 26S proteasome are known mediators but how their activities are linked is unclear. To better understand these mechanisms, a panel of model misfolded substrates was analyzed in detail. Surprisingly, their degradation occurs not in the cytosol but in the nucleus. Degradation is dependent on the E3 ubiquitin ligase San1p, known previously to direct the turnover of damaged nuclear proteins. A second E3 enzyme, Ubr1p, augments this activity but is insufficient by itself. San1p and Ubr1p are not required for nuclear import of substrates. Instead, the Hsp70 chaperone system is needed for efficient import and degradation. These data reveal a new function of the nucleus as a compartment central to the quality control of cytosolic proteins.
Inhibition of Aspergillus flavus in Soil by Antagonistic Pseudomonas Strains Reduces the Potential for Airborne Spore Dispersal
Authors: Palumbo Jeffrey D. , O'Keeffe Teresa L. , Kattan Ali , Abbas Hamed K. , Johnson Bobbie J.
Published: May 2010

Pseudomonas chlororaphis strain JP1015 and P. fluorescens strain JP2175 were previously isolated from Mississippi cornfield soil samples and selected for their growth inhibition of Aspergillus flavus in laboratory culture. In this study, the antifungal activity of these bacterial strains against A. flavus in soil coculture was determined. Growth of A. flavus was inhibited up to 100-fold by P. chlororaphis strain JP1015 and up to 58-fold by P. fluorescens strain JP2175 within 3 days following soil coinoculation. A. flavus propagule densities after 16 days remained 7- to 20-fold lower in soil treated with either bacterial strain. Using a bench-scale wind chamber, we demonstrated that treatments of soil with P. chlororaphis strain JP1015 and P. fluorescens strain JP2175 reduced airborne spores dispersed across a 1 m distance by 75- to 1,000-fold and 10- to 50-fold, respectively, depending on soil type and inoculum level. These results suggest that application of these bacterial strains may be effective in reducing soil populations of mycotoxigenic fungi, thereby reducing fungal spore formation, and ultimately reducing the potential for crop plant infection via airborne transmission.
Virulence Characteristics Accounting for Fire Blight Disease Severity in Apple Trees and Seedlings
Authors: Lee Steven A. , Ngugi Henry K. , Halbrendt Noemi O. , O'Keefe Grace , Lehman Brian , Travis James W. , Sinn Judith P. , McNellis Timothy W.
Published: May 2010

The gram-negative bacterium Erwinia amylovora is the causal agent of fire blight, the most destructive bacterial disease of rosaceous plants, including apple and pear. Here, we compared the virulence levels of six E. amylovora strains (Ea273, CFBP1367, Ea581a, E2002a, E4001a, and HKN06P1) on apple trees and seedlings. The strains produced a range of disease severity, with HKN06P1 producing the greatest disease severity in every assay. We then compared virulence characteristic expression among the six strains, including growth rates in immature apple fruit, amylovoran production, levansucrase activity, biofilm formation, carbohydrate utilization, hypersensitive cell death elicitation in tobacco leaves, and protein secretion profiles. Multiple regression analysis indicated that three of the virulence characteristics (amylovoran production, biofilm formation, and growth in immature apple fruit) accounted for >70% of the variation in disease severity on apple seedlings. Furthermore, in greenhouse-grown ‘Gala’ trees, >75% of the variation in disease severity was accounted for by five of the virulence characteristics: amylovoran production, biofilm formation, growth in immature apple fruit, hypersensitive cell death elicitation, and sorbitol utilization. This study demonstrates that virulence factor expression levels account for differences in disease severity caused by wild isolates of E. amylovora on apple trees.
Resistance to Tomato chlorosis virus in Wild Tomato Species that Impair Virus Accumulation and Disease Symptom Expression
Authors: García-Cano Elena , Navas-Castillo Jesús , Moriones Enrique , Fernández-Muñoz Rafael
Published: May 2010

Tomato chlorosis virus (ToCV) (genus Crinivirus, family Closteroviridae) is an emerging threat to tomato crops worldwide. Although symptoms on fruits are not obvious, yield losses occur through decreased fruit size and number. Control of ToCV epidemics is difficult because the virus is transmitted by several whitefly vector species and its relatively wide host range facilitates establishment in local wild reservoirs. Therefore, breeding for ToCV resistance offers the best control alternative. However, no sources for resistance are available thus far. Here, a screen of tomatoes and wild species relatives was performed in search of ToCV resistance. Two sources of resistance to ToCV were identified in this work, lines ‘802-11-1’ and ‘821-13-1’, each derived by two self-pollinations from ToCV asymptomatic plants of the population ‘IAC CN RT’ (derived from an interspecific hybrid Solanum lycopersicum × S. peruvianum accession LA0444) and accession LA1028 (S. chmielewskii), respectively. The resistance was expressed by impairing virus accumulation and disease symptom expression, both under natural infection and after challenging with ToCV in controlled inoculations. Genetic control of resistance to ToCV infection in ‘821-13-1’ was conferred by a major locus with mainly additive effects but also partial dominance for higher susceptibility. Also, an additive × dominance epistatic interaction with at least one additional gene was evident.
Daily Changes of Infections by Pythium ultimum After a Nutrient Impulse in Organic Versus Conventional Soils
Authors: He Miaomiao , Ma Wenjun , Tian Guangming , Blok Wim , Khodzaeva Anna , Zelenev Vladimir V. , Semenov Alexander M. , van Bruggen Ariena H. C.
Published: May 2010

Bacterial populations (CFU) have been shown to oscillate in wavelike patterns after nutrient impulses in previous studies. The amplitudes and periods of oscillations could possibly be used as indicators of soil health analogous to the stability and resilience of biological populations widely accepted as indicators for ecosystem health. Limited plant and animal disease outbreaks can also be viewed as a manifestation of a healthy soil ecosystem. Two pot experiments were carried out to verify whether damping-off of beet seedlings by Pythium ultimum, measured as area under the disease progress curve (AUDPC), fluctuated over time after incorporation of organic materials into organic versus conventional soils, and to investigate whether daily dynamics of AUDPCs were linked to the dynamics of microbial populations and chemical parameters. AUDPCs oscillated significantly over time when Pythium bioassays were initiated daily after addition of ground grass and clover shoots (GC) into unplanted soils. Similar oscillations with significant harmonics of AUDPC were also observed in composted manure (CM)-amended soils but with smaller amplitudes than in GC-amended soils. The AUDPC harmonics in amended soils had periods similar to those of CFU of copiotrophic bacteria. Cross-correlation analysis demonstrated that periodic fluctuations of P. ultimum infections (AUDPCs) did not coincide with those of copiotrophic CFU but were shifted in phase. It appears that competition or antagonism from some fast-growing bacteria influenced pathogen infections, because these bacterial populations were growing and dying. Soil chemical variables, including pH, dissolved organic carbon, and NO3−-N, and NH4+-N contents, changed significantly in the initial 7 days after a nutrient impulse into soils. These changes were cross-correlated with copiotrophic CFU with time lags of ≈1 to 2 days but were seldom associated with daily changes in AUDPCs. Organically managed soils always had lower AUDPC ratios of amended to nonamended treatments, indicating that organic materials showed stronger suppressive abilities to P. ultimum in organic than in conventional soils. The oscillations in AUDPCs and copiotrophic CFU in amended organic soil also had smaller amplitudes than in amended conventional soil. These results suggested that organically managed soils had a greater resistance and resilience to the disturbance of the amendments and, therefore, could be considered healthier than conventionally managed soils.
Multilocus Sequence Typing of Xylella fastidiosa Causing Pierce's Disease and Oleander Leaf Scorch in the United States
Authors: Yuan Xiaoli , Morano Lisa , Bromley Robin , Spring-Pearson Senanu , Stouthamer Richard , Nunney Leonard
Published: May 2010

Using a modified multilocus sequence typing (MLST) scheme for the bacterial plant pathogen Xylella fastidiosa based on the same seven housekeeping genes employed in a previously published MLST, we studied the genetic diversity of two subspecies, X. fastidiosa subsp. fastidiosa and X. fastidiosa subsp. sandyi, which cause Pierce's disease and oleander leaf scorch, respectively. Typing of 85 U.S. isolates (plus one from northern Mexico) of X. fastidiosa subsp. fastidiosa from 15 different plant hosts and 21 isolates of X. fastidiosa subsp. sandyi from 4 different hosts in California and Texas supported their subspecific status. Analysis using the MLST genes plus one cell-surface gene showed no significant genetic differentiation based on geography or host plant within either subspecies. Two cases of homologous recombination (with X. fastidiosa subsp. multiplex, the third U.S. subspecies) were detected in X. fastidiosa subsp. fastidiosa. Excluding recombination, MLST site polymorphism in X. fastidiosa subsp. fastidiosa (0.048%) and X. fastidiosa subsp. sandyi (0.000%) was substantially lower than in X. fastidiosa subsp. multiplex (0.240%), consistent with the hypothesis that X. fastidiosa subspp. fastidiosa and sandyi were introduced into the United States (probably just prior to 1880 and 1980, respectively). Using whole-genome analysis, we showed that MLST is more effective at genetic discrimination at the specific and subspecific level than other typing methods applied to X. fastidiosa. Moreover, MLST is the only technique effective in detecting recombination.
One of Two Major Paralogs of AVR-Pita1 Is Functional in Japanese Rice Blast Isolates
Authors: Takahashi Mami , Ashizawa Taketo , Hirayae Kazuyuki , Moriwaki Jouji , Sone Teruo , Sonoda Ryoichi , Noguchi Masako Tsujimoto , Nagashima Susumu , Ishikawa Kouji , Arai Michiyoshi
Published: May 2010

We analyzed the avirulence gene AVR-Pita1 in Japanese rice blast isolates to determine how they gain virulence toward rice cultivars containing the Pita resistance gene. An avirulent isolate, OS99-G-7a (G7a), from a Japanese commercial field contained two paralogs of AVR-Pita1, designated as AVR-Pita1JA and AVR-Pita1JB. Analysis of virulent, independent mutants derived from G7a, a single avirulent progenitor strain, indicated that AVR-Pita1JA was functional but AVR-Pita1JB was nonfunctional. The most frequent mutation was loss of AVR-Pita1JA. Analyses of field isolates collected from diverse areas in Japan revealed that most of the AVR-Pita1 genes carried by Japanese isolates were identical to AVR-Pita1JA or AVR-Pita1JB. The relationship between these major paralogs in Japanese isolates and the virulence of the strains carrying them indicate that AVR-Pita1JA is functional but AVR-Pita1JB is not, as is the case in G7a. Isolates that show virulence toward rice cultivars containing the Pita gene are presumed to have evolved virulence from avirulent origins via loss of AVR-Pita1JA, except for one case in which virulence resulted from a base substitution. In this study, we discuss the properties and specificities of Japanese rice blasts that relate to virulence against Pita-containing rice. Furthermore, we present a method to amplify AVR-Pita1JA and AVR-Pita1JB separately and, specifically, to monitor functional AVR-Pita1 in Japan.
Resistance in Tomato and Wild Relatives to Crown and Root Rot Caused by Phytophthora capsici
Authors: Quesada-Ocampo L. M. , Hausbeck M. K.
Published: May 2010

Phytophthora capsici causes root, crown, and fruit rot of tomato, a major vegetable crop grown worldwide. The objective of this study was to screen tomato cultivars and wild relatives of tomato for resistance to P. capsici. Four P. capsici isolates were individually used to inoculate 6-week-old seedlings (1 g of P. capsici-infested millet seed per 10 g of soilless medium) of 42 tomato cultivars and wild relatives of tomato in a greenhouse. Plants were evaluated daily for wilting and death. All P. capsici isolates tested caused disease in seedlings but some isolates were more pathogenic than others. A wild relative of cultivated tomato, Solanum habrochaites accession LA407, was resistant to all P. capsici isolates tested. Moderate resistance to all isolates was identified in the host genotypes Ha7998, Fla7600, Jolly Elf, and Talladega. P. capsici was frequently recovered from root and crown tissue of symptomatic inoculated seedlings but not from leaf tissue or asymptomatic or control plants. The phenotype of the recovered isolate matched the phenotype of the inoculum. Pathogen presence was confirmed in resistant and moderately resistant tomato genotypes by species-specific polymerase chain reaction of DNA from infected crown and root tissue. Amplified fragment length polymorphisms of tomato genotypes showed a lack of correlation between genetic clusters and susceptibility to P. capsici, indicating that resistance is distributed in several tomato lineages. The results of this study create a baseline for future development of tomato cultivars resistant to P. capsici.
Condition-dependent ecdysis and immunocompetence in the amphipod crustacean,
Gammarus pulex
Authors: Moret Yannick , Rigaud Thierry , Motreuil Sébastien , Troussard Jean-Phillipe , Moreau Jérôme
Published: May 2010

The exoskeleton of arthropods forms an efficient protection against pathogens, but this first line of defence is periodically weakened during ecdysis, increasing the opportunity for surrounding pathogens to invade the body cavity. Since the richness of pathogens in the environment can be spatially and temporally variable, arthropods may have a fitness advantage in moulting in a place and time of low infection risk. Consistent with this hypothesis, we found that the amphipod crustacean,
Gammarus pulex
, exhibits temporal adjustment of the moult cycle in response to elevated risks of infection. Interestingly, this phenomenon is variable between two populations and independent of levels of immune defences. These results suggest that plasticity of the moult cycle in response to elevated risks of infection is adaptive and may result from adaptation to local variations in the risk of infection.
Is group size related to longevity in mammals?
Authors: Kamilar Jason M. , Bribiescas Richard G. , Bradley Brenda J.
Published: May 2010

Life-history theory predicts that reduced extrinsic risk of mortality should increase species longevity over evolutionary time. Increasing group size should reduce an individual's risk of predation, and consequently reduce its extrinsic risk of mortality. Therefore, we should expect a relationship between group size and maximum longevity across species, while controlling for well-known correlates of longevity. We tested this hypothesis using a dataset of 253 mammal species and phylogenetic comparative methods. We found that group size was a poor predictor of maximum longevity across all mammals, as well as within primates and rodents. We found a weak but significant group-size effect on artiodactyl longevity, but in a negative direction. Body mass was consistently the best predictor of maximum longevity, which may be owing to lower predation risk and/or lower basal metabolic rates for large species. Artiodactyls living in large groups may exhibit higher rates of extrinsic mortality because of being more conspicuous to predators in open habitats, resulting in shorter lifespans.
Food-web structure in low- and high-dimensional trophic niche spaces
Authors: Rossberg Axel G. , Brännström Åke , Dieckmann Ulf
Published: May 2010

A question central to modelling and, ultimately, managing food webs concerns the dimensionality of trophic niche space, that is, the number of independent traits relevant for determining consumer–resource links. Food-web topologies can often be interpreted by assuming resource traits to be specified by points along a line and each consumer's diet to be given by resources contained in an interval on this line. This phenomenon, called intervality, has been known for 30 years and is widely acknowledged to indicate that trophic niche space is close to one-dimensional. We show that the degrees of intervality observed in nature can be reproduced in arbitrary-dimensional trophic niche spaces, provided that the processes of evolutionary diversification and adaptation are taken into account. Contrary to expectations, intervality is least pronounced at intermediate dimensions and steadily improves towards lower- and higher-dimensional trophic niche spaces.
Surface-enhanced Raman scattering biomedical applications of plasmonic colloidal particles
Authors: Abalde-Cela Sara , Aldeanueva-Potel Paula , Mateo-Mateo Cintia , Rodríguez-Lorenzo Laura , Alvarez-Puebla Ramón A. , Liz-Marzán Luis M.
Published: May 2010

This review article presents a general view of the recent progress in the fast developing area of surface-enhanced Raman scattering spectroscopy as an analytical tool for the detection and identification of molecular species in very small concentrations, with a particular focus on potential applications in the biomedical area. We start with a brief overview of the relevant concepts related to the choice of plasmonic nanostructures for the design of suitable substrates, their implementation into more complex materials that allow generalization of the method and detection of a wide variety of (bio)molecules and the strategies that can be used for both direct and indirect sensing. In relation to indirect sensing, we devote the final section to a description of SERS-encoded particles, which have found wide application in biomedicine (among other fields), since they are expected to face challenges such as multiplexing and high-throughput screening.
Unsteady motion: escape jumps in planktonic copepods, their kinematics and energetics
Authors: Kiørboe Thomas , Andersen Anders , Langlois Vincent J. , Jakobsen Hans H.
Published: May 2010

We describe the kinematics of escape jumps in three species of 0.3–3.0 mm-sized planktonic copepods. We find similar kinematics between species with periodically alternating power strokes and passive coasting and a resulting highly fluctuating escape velocity. By direct numerical simulations, we estimate the force and power output needed to accelerate and overcome drag. Both are very high compared with those of other organisms, as are the escape velocities in comparison to startle velocities of other aquatic animals. Thus, the maximum weight-specific force, which for muscle motors of other animals has been found to be near constant at 57 N (kg muscle)−1, is more than an order of magnitude higher for the escaping copepods. We argue that this is feasible because most copepods have different systems for steady propulsion (feeding appendages) and intensive escapes (swimming legs), with the muscular arrangement of the latter probably adapted for high force production during short-lasting bursts. The resulting escape velocities scale with body length to power 0.65, different from the size-scaling of both similar sized and larger animals moving at constant velocity, but similar to that found for startle velocities in other aquatic organisms. The relative duration of the pauses between power strokes was observed to increase with organism size. We demonstrate that this is an inherent property of swimming by alternating power strokes and pauses. We finally show that the Strouhal number is in the range of peak propulsion efficiency, again suggesting that copepods are optimally designed for rapid escape jumps.
CIR versus CME drivers of the ring current during intense magnetic storms
Authors: Liemohn Michael W. , Jazowski Matt , Kozyra Janet U. , Ganushkina Natalia , Thomsen Michelle F. , Borovsky Joseph E.
Published: May 2010

Ninety intense magnetic storms (minimum Dst value of less than −100 nT) from solar cycle 23 (1996–2005) were simulated using the hot electron and ion drift integrator (HEIDI) model. All 90 storm intervals were run with several electric fields and nightside plasma boundary conditions (five run sets). Storms were classified according to their solar wind driver, including corotating interaction regions (CIRs) and interplanetary coronal mass ejections (ICMEs). Data-model comparisons were made against the observed Dst index (specifically, Dst*) and dayside hot-ion measurements from geosynchronous orbiting spacecraft. It is found that the data-model goodness-of-fit values are different for CIR-driven storms relative to ICME-driven storms. The results are also different for the same storm category for different boundary conditions. None of the CIR-driven events was overpredicted by HEIDI, while the dayside comparisons were comparable for the different drivers. The results imply that the outer magnetosphere is responding differently to the two kinds of solar wind drivers, even though the resulting storm size might be similar. That is, for ICME-driven events, magnetospheric currents inside of geosynchronous orbit dominate the Dst perturbation, while for CIR-driven events, currents outside of this boundary have a systematically larger contribution.
Extraordinary ductility in Al-bearing δ-TRIP steel
Authors: Yi H. L. , Lee K. Y. , Bhadeshia H. K. D. H.
Published: May 2010

An iron-based alloy system has been developed that exhibits impressive combinations of tensile strength and elongation that are not available with current steels used in the manufacture of automobiles. Furthermore, the heat treatments required to achieve these properties are consistent with practical production processes. The alloys rely on significant concentrations of ferrite-stabilizing solutes so that δ-ferrite which forms during solidification is retained in the microstructure.
Intraspecific genetic variation and competition interact to influence niche expansion
Authors: Agashe Deepa , Bolnick Daniel I.
Published: May 2010

Theory and empirical evidence show that intraspecific competition can drive selection favouring the use of novel resources (i.e. niche expansion). The evolutionary response to such selection depends on genetic variation for resource use. However, while genetic variation might facilitate niche expansion, genetically diverse groups may also experience weaker competition, reducing density-dependent selection on resource use. Therefore, genetic variation for fitness on different resources could directly facilitate, or indirectly retard, niche expansion. To test these alternatives, we factorially manipulated both the degree of genetic variation and population density in flour beetles (Tribolium castaneum) exposed to both novel and familiar food resources. Using stable carbon isotope analysis, we measured temporal change and individual variation in beetle diet across eight generations. Intraspecific competition and genetic variation acted on different components of niche evolution: competition facilitated niche expansion, while genetic variation increased individual variation in niche use. In addition, genetic variation and competition together facilitated niche expansion, but all these impacts were temporally variable. Thus, we show that the interaction between genetic variation and competition can also determine niche evolution at different time scales.
Testing the heterospecific attraction hypothesis with time-series data on species co-occurrence
Authors: Sebastián-González Esther , Sánchez-Zapata José Antonio , Botella Francisco , Ovaskainen Otso
Published: May 2010

The distributional patterns of actively moving animals are influenced by the cues that the individuals use for choosing sites into which they settle. Individuals may gather information about habitat quality using two types of strategies, either directly assessing the relevant environmental factors, or using the presence of conspecifics or heterospecifics as an indirect measure of habitat quality. We examined patterns of heterospecific attraction with observational time-series data on a community of seven waterbird species breeding in artificial irrigation ponds. We fitted to the data a multivariate logistic regression model, which attributes the presence–absence of each species to a set of environmental and spatial covariates, to the presence of con- and heterospecifics in the previous year and to the presence of heterospecifics in the same year. All species showed a clear tendency to continue breeding in the same sites where they were observed in the previous year. Additionally, the presence of heterospecifics, both in the previous year and in the same year, generally increased the probability that the focal species was found breeding on a given pond. Our data thus give support for the heterospecific attraction hypothesis, though causal inference should be confirmed with manipulative experiments.
Evidence for competition between carnivorous plants and spiders
Authors: Jennings David E. , Krupa James J. , Raffel Thomas R. , Rohr Jason R.
Published: May 2010

Several studies have demonstrated that competition between disparate taxa can be important in determining community structure, yet surprisingly, to our knowledge, no quantitative studies have been conducted on competition between carnivorous plants and animals. To examine potential competition between these taxa, we studied dietary and microhabitat overlap between pink sundews (Drosera capillaris) and wolf spiders (Lycosidae) in the field, and conducted a laboratory experiment examining the effects of wolf spiders on sundew fitness. In the field, we found that sundews and spiders had a high dietary overlap with each other and with the available arthropod prey. Associations between sundews and spiders depended on spatial scale: both sundews and spiders were found more frequently in quadrats with more abundant prey, but within quadrats, spiders constructed larger webs and located them further away from sundews as the total sundew trapping area increased, presumably to reduce competition. Spiders also constructed larger webs when fewer prey were available. In the laboratory, our experiment revealed that spiders can significantly reduce sundew fitness. Our findings suggest that members of the plant and animal kingdoms can and do compete.
Less is more: density influences the development of behavioural life skills in trout
Authors: Brockmark S. , Adriaenssens B. , Johnsson J. I.
Published: May 2010

Theory suggests that habitat structure and population density profoundly influence the phenotypic development of animals. Here, we predicted that reduced rearing density and increased structural complexity promote food search ability, anti-predator response and the ability to forage on novel prey, all behavioural skills important for surviving in the wild. Brown trout were reared at three densities (conventional hatchery density, a fourth of conventional hatchery density and natural density) in tanks with or without structure. Treatment effects on behaviour were studied on trout fry and parr, whereupon 20 trout from each of the six treatment groups were released in an enclosed natural stream and recaptured after 36 days. Fry reared at natural density were faster to find prey in a maze. Moreover, parr reared at natural density were faster to eat novel prey, and showed more efficient anti-predator behaviour than fish reared at higher densities. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high density. In contrast, we found no clear treatment effects of structure. These novel results suggest that reduced rearing densities can facilitate the development of behavioural life skills in captive animals, thereby increasing their contribution to natural production.
Social vocalizations can release oxytocin in humans
Authors: Seltzer Leslie J. , Ziegler Toni E. , Pollak Seth D.
Published: May 2010

Vocalizations are important components of social behaviour in many vertebrate species, including our own. Less well-understood are the hormonal mechanisms involved in response to vocal cues, and how these systems may influence the course of behavioural evolution. The neurohormone oxytocin (OT) partly governs a number of biological and social processes critical to fitness, such as attachment between mothers and their young, and suppression of the stress response after contact with trusted conspecfics. Rodent studies suggest that OT's release is contingent upon direct tactile contact with such individuals, but we hypothesized that vocalizations might be capable of producing the same effect. To test our hypothesis, we chose human mother–daughter dyads and applied a social stressor to the children, following which we randomly assigned participants into complete contact, speech-only or no-contact conditions. Children receiving a full complement of comfort including physical, vocal and non-verbal contact showed the highest levels of OT and the swiftest return to baseline of a biological marker of stress (salivary cortisol), but a strikingly similar hormonal profile emerged in children comforted solely by their mother's voice. Our results suggest that vocalizations may be as important as touch to the neuroendocrine regulation of social bonding in our species.
Experimental evidence for limited vocal recognition in a wild primate: implications for the social complexity hypothesis
Authors: Bergman Thore J.
Published: May 2010

Although monitoring social information is a key aspect of the social complexity hypothesis, surprisingly little work has compared social knowledge across different species of wild animals. In the present study, I use playback experiments to test for individual recognition in wild male geladas (Theropithecus gelada) to compare with published accounts of social knowledge in chacma baboons (Papio ursinus). Geladas and baboons are closely related primates living in socially complex groups that differ dramatically in group size—geladas routinely associate with more than 10 times the number of conspecifics than do baboons. Using grunts from non-rival males to simulate approaches, I examined the strength of a subject male's response when the ‘approach’ was from the direction of (i) non-rival males (control), or (ii) rival males (a more salient stimulus if playback grunts are not recognized by the subject). I compared responses separately based on the degree of social overlap between the caller and the subject. Responses indicate that male geladas, unlike baboons, do not use vocalizations to recognize all of the individuals they regularly encounter. This represents, to my knowledge, the first documented evidence of ‘missing’ social knowledge in a natural primate population. The sharp distinction between baboons and geladas suggests that geladas are either unable or unmotivated to keep track of the individual identity of other males in their multi-level society—even males with whom they have a large degree of social overlap. Thus, these results are consistent with the central assumption of the social complexity hypothesis that social cognition is costly.
Contest outcome in a territorial butterfly: the role of motivation
Authors: Bergman Martin , Olofsson Martin , Wiklund Christer
Published: May 2010

In many butterfly species, males compete over areas advantageous for encountering females. Rules for contest settlement are, however, largely unknown and neither morphological nor physiological traits can reliably predict the contest outcome. Here, we test the hypothesis that contests are settled in accordance with a motivation asymmetry. We staged contests between males of
Pararge aegeria
and after removing the resident, the non-resident was allowed (i) either to interact with a non-receptive female for 30 min (
n
= 30) or (ii) to spend 30 min alone in the cage (
n
= 30), after which the initial resident was reintroduced. The results show that males that had interacted with a female had a higher probability of becoming dominant and reversing contest outcome. Moreover, males that were faster to take over a vacant territory when the resident was removed were more likely to become dominant. Here, we show for the first time, to our knowledge, that frequent encounters with a mated female can increase male motivation to persist in a territorial contest in a butterfly. Further, we suggest that variation in intrinsic motivation reflects male eagerness to take over vacant territory. This study indicates that variation in resource value and motivational asymmetries are important for settling contests in butterflies.
Upside-down spiders build upside-down orb webs: web asymmetry, spider orientation and running speed in
Cyclosa
Authors: Nakata Kensuke , Zschokke Samuel
Published: May 2010

Almost all spiders building vertical orb webs face downwards when sitting on the hubs of their webs, and their webs exhibit an up–down size asymmetry, with the lower part of the capture area being larger than the upper. However, spiders of the genus
Cyclosa
, which all build vertical orb webs, exhibit inter- and intraspecific variation in orientation. In particular,
Cyclosa ginnaga
and
C. argenteoalba
always face upwards, and
C. octotuberculata
always face downwards, whereas some
C. confusa
face upwards and others face downwards or even sideways. These spiders provide a unique opportunity to examine why most spiders face downwards and have asymmetrical webs. We found that upward-facing spiders had upside-down webs with larger upper parts, downward-facing spiders had normal webs with larger lower parts and sideways-facing spiders had more symmetrical webs. Downward-facing
C. confusa
spiders were larger than upward- and sideways-facing individuals. We also found that during prey attacks, downward-facing spiders ran significantly faster downwards than upwards, which was not the case in upward-facing spiders. These results suggest that the spider's orientation at the hub and web asymmetry enhance its foraging efficiency by minimizing the time to reach prey trapped in the web.
Male-specific (
Z
)-9-tricosene stimulates female mating behaviour in the spider
Pholcus beijingensis
Authors: Xiao Yong-Hong , Zhang Jian-Xu , Li Shu-Qiang
Published: May 2010

Chemical signals play an important role in spider sexual communication, yet the chemistry of spider sex pheromones remains poorly understood. Chemical identification of male-produced pheromone-mediating sexual behaviour in spiders has also, to our knowledge, not been reported before. This study aimed to examine whether chemically mediated strategies are used by males of the spider
Pholcus beijingensis
for increasing the probability of copulation. Based on data from gas chromatography–mass spectrometry analysis, electroantennography assay and a series of behavioural tests, we verified that (
Z
)-9-tricosene is a male-specific compound in the spider
P. beijingensis
. This compound acts as an aphrodisiac: it increases the likelihood that a female will mate. Mate-searching males release (
Z
)-9-tricosene to stimulate sexual behaviour of conspecific females. In the two-choice assay, however, sexually receptive females show no preference to the chambers containing (
Z
)-9-tricosene. This indicates that the male pheromone of
P. beijingensis
is not an attractant
per se
to the conspecific females. This is, to our knowledge, the first identification of a male-produced aphrodisiac pheromone in spiders.
Efa-1/LifA mediates intestinal colonization of calves by enterohaemorrhagic Escherichia coli O26 : H– in a manner independent of glycosyltransferase and cysteine protease motifs or effects on type III secretion
Authors: Deacon Victoria , Dziva Francis , van Diemen Pauline M. , Frankel Gad , Stevens Mark P.
Published: May 2010

Enterohaemorrhagic Escherichia coli (EHEC) comprise a group of animal and zoonotic pathogens of worldwide importance. Our previous research established that intestinal colonization of calves by EHEC serotypes O5 : H– and O111 : H– requires EHEC factor for adherence (Efa-1), also known as lymphostatin (LifA). Towards an understanding of the mode of action of Efa-1/LifA, chromosomal in-frame deletions of predicted glycosyltransferase (DXD) and cysteine protease (CHD) motifs were created in a Δstx1 derivative of EHEC O26 : H–. The magnitude and duration of faecal excretion of EHEC O26 : H– were significantly reduced by null mutation of efa-1/lifA, but were not impaired by ΔDXD or ΔCHD mutations, in contrast to observations made with truncated Efa-1/LifA mutants of Citrobacter rodentium in mice. Although C. rodentium Efa-1/LifA influences the induction of colonic hyperplasia in mice, EHEC O26 : H– Efa-1/LifA was not required for fluid accumulation or neutrophil recruitment in bovine ileal loops. In contrast to observations with EHEC O5 : H– or O111 : H– mutants, inactivation of efa-1/lifA in EHEC O26 : H– did not significantly affect adherence or secretion of type III secreted proteins that play pivotal roles in calf colonization. Lymphostatin activity could not be reliably demonstrated in lysates of EHEC O26 : H–; however, deletion of the glycosyltransferase and cysteine protease motifs in Efa-1/LifA from enteropathogenic E. coli O127 : H6 abolished lymphostatin activity. Our data uncouple the role of Efa-1/LifA in calf colonization from effects on type III secretion and reinforce the potential for pathotype- and serotype-specific phenotypes.