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The ON and OFF ORNs on cockroach antennae optimize the detection and transfer of information about concentration increments and decrements by providing excitatory responses for both. It follows that the antagonism of the responses facilitates instantaneous evaluations of the odor plume to help the insect make tracking decisions by signaling "higher concentration than background" and "lower concentration than background". Here we analyzed the effect of the background concentration level of the odor of lemon oil on the responses of the ON and OFF ORNs to jumps and drops of that odor, respectively. Raising the background level decreases both the ON-ORN's response to concentration jumps and the OFF-ORN's response to concentration drops. Impulse frequency of the ON ORN is high when the concentration jump is large, but for a given jump, frequency tends to be higher when the background level is low. Conversely, impulse frequency of the OFF cell is high at large concentration drops, but higher still when the background level is low. Analyses of this double dependence revealed that the activity of both types of ORNs is raised more by increasing the change in concentration than by decreasing the background concentration by the same amount. This effect is greater in the OFF ORN than in the ON ORN, indicating a bias for falling concentrations. Given equal change in concentration, concentration drops evoke stronger responses in the OFF ORN than concentrations jumps in the ON ORN. This suggests that the OFF responses are used as alert information for accurately tracking. [ABSTRACT FROM AUTHOR]

The risk of exposure to radioactive elements is seldom assessed considering mixture toxicity, potentially over- or underestimating biological and ecological effects on ecosystems. This study investigated how three end points, carbon transfer between phytoplankton and Daphnia magna, D. magna mobility and growth, responded to exposure to γ-radiation in combination with the heavy metal cadmium (Cd), using the MIXTOX approach. Observed effects were compared with mixture effects predicted by concentration addition (CA) and independent action (IA) models and with deviations for synergistic/antagonistic (S/A), dose-level (DL), and dose-ratio (DR) dependency interactions. Several patterns of response were observed depending on the end point tested. DL-dependent deviation from the IA model was observed for carbon incorporation with antagonism switching to synergism at higher doses, while the CA model indicated synergism, mainly driven by effects at high doses of γ-radiation. CA detected antagonism regarding acute immobilization, while IA predicted DR-dependency. Both CA and IA also identified antagonism for daphnid growth. In general, effects of combinations of γ-radiation and Cd seem to be antagonistic at lower doses, but synergistic at the higher range of the doses tested. Our results highlight the importance of investigating the effects of exposure to γ-radiation in a multistressor context. [ABSTRACT FROM AUTHOR]

This article sets up a conversation with Frantz Fanon about his stretching of dialectics. Against a backdrop where multiple dominant epistemologies of political theory and international relations presume and are shaped by a segregation of the world into anarchy and the desire for an ordered global, Fanon's reading of imperialism's effects in theWretched of the Earthis of utmost relevance. First, Fanon's work allows us to think dialectics along with ‘globality’ and to confronting dominant presumptions about a Manichean world: anarchy, order, and ‘bodies.’ He focuses on colonization and the White–Black relation and the radical dehumanization of the Other (Black, colonial slave, non-European, etc.). Second, his engagement of colonial violence pushes him to stretch dialectics, reactivating the ‘partially neutralized antagonisms.’ In addition, Fanon wants to think revolutionary practice as a kind of internationalism which will reunite into its own humanness in an open-ended-way—a world where no human being will be subject to dehumanization. I conclude with some ideas on what a revolutionary thinking about a revolutionary subjectivity, movement and thought entails for revolutionary struggles and dialectics today. [ABSTRACT FROM PUBLISHER]

Studying interactions of multiple pesticides applied simultaneously in a mixture is a common task in phytopathology. Statistical methods are employed to test whether the treatment components influence each other's efficacy in a promotive or inhibitory way (synergistic or antagonistic interaction) or rather act independent of one another (additivity). The trouble is that widely used procedures based on chi-square tests are often seriously flawed, either because people apply them in a preposterous way or because the method simply does not fit the problem at hand. Browsing recent volumes of entomological journals, we found that numerous researchers have (in all likelihood unwittingly) analysed their data as if they had had a sample size of 100 or, equally bad, a sample size of one! We show how to avoid such poor practices and further argue that chi-square testing is, even if applied correctly (meaning that no technical errors are made), a limited purpose tool for assessing treatment interactions. [ABSTRACT FROM AUTHOR]

This study was conducted to estimate the potential of Bacillus pumilus L1 against root-knot nematode, Meloidogyne arenaria, in both in vitro and in vivo conditions. B. pumilus L1 was found to produce both protease and chitinase. When various concentrations (1-10%) of the bacterial culture (BC) or 0.02-0.11 mg/ml of the crude enzymes produced by B. pumilus L1 were used to treat M. arenaria eggs and second-stage juveniles (J2), inhibition of hatching and J2 mortality were significantly increased under in vitro conditions. In addition, the hatching inhibition and J2 mortality rate were improved with increasing concentrations of BC and the crude enzymes. Similarly, these effects also increased over time after treatment with BC. Moreover, the crude enzymes caused partial degradation of the eggshell and juvenile body when treated at 0.11 mg/ml. The pot experiment also demonstrated that the application of BC to potted soil caused significant reduction in the number of galls and egg masses in the plant roots and of the J2 population as compared to the untreated control 6 weeks after M. arenaria infestation. In addition, the simultaneous application of BC upon nematode inoculation proved more effective than application 2 days postinoculation with nematode. B. pumilus L1 inoculation (BC, BCs and BC2) also promoted tomato plant growth as compared to the controls (TW, Ne, GM and NeT). Thus, our results demonstrated the ability of B. pumilus L1 as a potential biocontrol agent against root-knot nematode, with additional activity as a plant growth promoter for tomato. [ABSTRACT FROM AUTHOR]

Chaetomium globosum and Trichoderma harzianum were isolated from healthy tomato plants at the rhizospheric area. These isolates were evaluated as potential bio-agents in control of the soil-borne fungi, Fusarium solani the causal agent of root rot, Fusarium oxysporum f. sp. lycopersici, Fusarium oxysporum f. sp. radicis-lycopersici and Fusarium semitectum were isolated from diseased tomato plants in Alexandria and Giza Governorates. The Pathogenicity test on tomato plant was conducted under greenhouse conditions. It indicated that, all tested fungi have a pathogenic effect on tomato plant. After one week the death percentages caused by F. solani, F. oxysporum f. sp. lycopersici, F. oxysporum f. sp. radicis-lycopersici and F. semitectum were 43.8, 31.3, 68.8 and 56.3%, respectively. However, after 45 days, the obtained data percentages for the same fungi were 62.5, 73, 87.5 and 83.8, respectively. The tested bio-agents affected all tested pathogens ,however, C. globosum at zero time of the pathogen inoculation reduced the radial growth of F. oxysporum f. sp. lycopersici, F. oxysporum f. sp. radicis-lycopersici, F. semitectum and F. solani by 53, 24.4, 48.9 and 22.2%, respectively, while C. globosum (3 days before the pathogen inoculation) reduced the radial growth of F. oxysporum f. sp. lycopersici, F. oxysporum f. sp. radicislycopersici, F. semitectum and F. solani by 68.9, 48.9, 72.2 and 38.8%, respectively, on the other hand, T. harzianum reduced the radial growth of the same tested pathogens (F. oxysporum f. sp. lycopersici, F. oxysporum f. sp. radicis-lycopersici, F. semitectum and F. solani ) by 66.7, 67.8, 100 and 61.1, respectively. T. harzianum was the most effective bio-agent against Fusarium spp. Comparing with C. globosum. It had recorded the complete growth reduction When it had been tested on Fusarium semitectum with 100% percentage. [ABSTRACT FROM AUTHOR]

Host-parasite interactions are often characterized by large fluctuations in host population size, and we investigated how such host bottlenecks affected coevolution between a bacterium and a virus. Previous theory suggests that host bottlenecks should provide parasites with an evolutionary advantage, but instead we found that phages were rapidly driven to extinction when coevolving with hosts exposed to large genetic bottlenecks. This was caused by the stochastic loss of sensitive bacteria, which are required for phage persistence and infectivity evolution. Our findings emphasize the importance of feedbacks between ecological and coevolutionary dynamics, and how this feedback can qualitatively alter coevolutionary dynamics. [ABSTRACT FROM AUTHOR]

The research was conducted during 2010 - 2012 on pellic vertisol soil type. A field experiment was carried out with durum wheat cultivar Progress (Triticum durum var. leucurum Desf.). Factor A included the years of investigation. Factor B included no treated check and 3 retardants - Cycocel extra (chlormequat + cholinechloride) - 1.5 l/ha, Vivax (chlormequat + ethephon) - 1.7 l/ha, Terpal (ethephon + mepiquat) - 3 l/ha. Factor C included weeded no treated check and 4 antibroadleaved herbicides - Granstar 75 DF (tribenuron-methyl) - 20 g/ha, Granstar super 50 SG (tribenuron-methyl + tiphensulfuron-methyl) - 40 g/ha, Laren 20 SG (methsulfuron-methyl) - 30 g/ha, Ally max SG (methsulfuron-methyl + tribenuron-methyl) - 35 g/ha. All of retardants, antibroadleaved herbicides and their tank mixtures were treated in tillering stage of the durum wheat. The weak adhesion of Granstar, Granstar super, Laren and Ally max required its application with adjuvant Trend 90 - 0.1%. Herbicide Granstar super cannot be mixed with retardants containing chlormequat - Cycocel extra and Vivax. There is antagonism at mixtures of retardant Terpal with herbicides containing methsulfuron-methyl - Laren and Ally max. The lowest durum wheat grain yields are obtained by these tank mixtures. Tank mixtures of herbicide Granstar super with retardants Cycocel extra and Vivax and retardant Terpal with herbicides Laren and Ally max are the most unstable for grain yield. Tank mixtures of retardants Cycocel extra and Vivax with herbicides Ally max, Laren and Granstar and of retardant Terpal with herbicides Granstar super and Granstar are technological the most valuable. They combine high grain yield with high stability with relation to different years. Self-use of retardants Cycocel extra, Vivax and Terpal without herbicides have low estimate and do not be used in the durum wheat crops. [ABSTRACT FROM AUTHOR]

The “Lévy Foraging Hypothesis” promotes Lévy walk (LW) as the best strategy to forage for patchily but unpredictably located prey. This strategy mixes extensive and intensive searching phases in a mostly cue-free way through strange, scale-free kinetics. It is however less efficient than a cue-driven two-scale Composite Brownian walk (CBW) when the resources encountered are systematically detected. Nevertheless, it could be assumed that the intrinsic capacity of LW to trigger cue-free intensive searching at random locations might be advantageous when resources are not only scarcely encountered but also so cryptic that the probability to detect those encountered during movement is low. Surprisingly, this situation, which should be quite common in natural environments, has almost never been studied. Only a few studies have considered “saltatory” foragers, which are fully “blind” while moving and thus detect prey only during scanning pauses, but none of them compared the efficiency of LW vs. CBW in this context or in less extreme contexts where the detection probability during movement is not null but very low. In a study based on computer simulations, we filled the bridge between the concepts of “pure continuous” and “pure saltatory” foraging by considering that the probability to detect resources encountered while moving may range from 0 to 1. We showed that regularly stopping to scan the environment can indeed improve efficiency, but only at very low detection probabilities. Furthermore, the LW is then systematically outperformed by a mixed cue-driven/internally-driven CBW. It is thus more likely that evolution tends to favour strategies that rely on environmental feedbacks rather than on strange kinetics. [ABSTRACT FROM AUTHOR]

Herb and legume mixes have been shown to increase animal performance compared with perennial ryegrass/white clover. The objective of this experiment was to determine the response of a herb and legume mix containing chicory (Cichorium intybus), plantain (Plantago lanceolata), red clover (Trifolium pratense) and white clover (T. repens) to either Hard (post-grazing residual of 4 cm) or Lax (post-grazing residual of 8 cm) grazing treatments using a 3–5 week grazing cycle with sheep over 2 years. The sward produced a greater dry matter yield under Hard than Lax grazing (11.6 vs 8.9 t DM/ha/year). However, Lax grazing maintained all four species in the sward, with a greater red clover contribution to the sward. Chicory had a greater taproot diameter and root water-soluble carbohydrate concentration under Lax than Hard grazing. Overall, this study illustrates that the herb and legume mix is likely to be more persistent under Lax than Hard grazing. [ABSTRACT FROM PUBLISHER]

Predation and competition are highly influential factors determining space use in foraging animals, and ultimately contribute to the spatial heterogeneity observed within habitats. Here we investigated the influence of competition and predation on space and resource use via continuous video transect observations - a tool that has not previously been employed for this purpose. This study therefore also evaluates video data as a pragmatic tool to study community interactions in the deep sea. Observations were compiled from 15 video transects spanning five submarine canyons in the Bay of Biscay, France. Substrate choice, positioning on the coral, echinoid aggregate size, and the presence/ absence of predators (e.g. fish and decapods) as well as competitors (both interand intra-specific) were recorded. Two dominant co-existing echinoid taxa, echinothurids and Cidaris cidaris (3188 total observations), were observed in the study. For the echinothurids, no significant trends were detected in the interand intra-specific competition data. For Cidaris cidaris, significant shifts in substrate use were correlated to the presence of inter-specific competitors (echinothurids), whereby an increase in dead coral substrate usage was observed. Highly significant patterns were detected amongst echinoids near fish and decapod predators. A shift to the base of the coral infra-structure was correlated to the presence of fish, and fewer individuals were observed in the open areas of the reef and a greater number were found in the mid and top sections of the coral when in the presence of decapods. Aggregates formed irrespective of the presence of predators. Aggregations are likely to form for feeding and reproduction rather than for defensive purposes; and migration along the coral infra-structure may be a predator-driven behaviour as echinoids seek refuge from predators. Predation risk might play a stronger - or more detectable - role in structuring echinoid space and resource use in deep-sea coral habitats. In addition, the study successfully detected patterns in the video data thereby demonstrating its potential usefulness for similar ecological studies on other deep-dwelling megabenthos. [ABSTRACT FROM AUTHOR]

This paper examines the increasingly popular approach of militant research and argues for the need to conceptualise it as a contradictory approach that exists against-and-beyond any form it takes. It understands militant research as a committed and intense process of internal reflection from within particular struggle(s) that seeks to map out and discuss underlying antagonisms while pushing the movement forward. Based on the author's experiences of doing militant research with Occupy London from both inside the university and through the Occupy Research Collective created outside, it argues that there are no ideal sites for doing militant research. It explores the opportunities of doing militant research within the university, pointing towards the potential for subverting the resources available, and highlights the barriers, in particular with relation to ethics. The Occupy Research Collective ( ORC) is then examined as an alternative space for doing militant research. In turn, a number of limitations of ORC are noted, including both its lack of resources and tendency to (re)create a form of doing militant research detached from broader struggles. While recent work has highlighted the need for militant research to operate antagonistically to the neoliberal university, and there have been calls to create new institutions outside it, this paper extends previous arguments by emphasising the need to criticise all forms of militant research in order to push struggles forward. It draws on John Holloway's widely referenced 'in-against-and-beyond' dialectical approach to emphasise the inevitable challenges of institutionalising militant research, no matter where this takes place. It concludes by suggesting that militant research should not shy away from embracing critiques of particular struggles and that further theoretical work needs to be done in terms of developing a more open and relational understanding of militancy. [ABSTRACT FROM AUTHOR]

This article describes a rapid strategic environmental assessment (SEA) of Namibia's Fourth National Development Plan (NDP4) (2012–2013 to 2016–2017). The authors believe this to be the first application of such an approach to a national development plan that typically charts a country's key over-arching development objectives and targets. It was undertaken over four weeks and involved a preparatory desk review of the objectives and implementation strategies of NDP4, Vision-2030 and key sector policies, as well as several other policies. The results were analysed during half-day, facilitated, multi-stakeholder focus sessions convened for each of five policy clusters that drive development in Namibia: land and agriculture, water, conservation and tourism, mining and industry, and fisheries. Policy performance and synergies/antagonisms within and between policies were assessed, and how policy elements might be improved to enhance synergies/reduce antagonisms and improve their contribution to sustainable development and achieve the goals of NDP4 and Vision-2030. This rapid approach to SEA offers a cost-effective alternative to conventional SEA requiring many months, a team of experts and an extensive process. [ABSTRACT FROM PUBLISHER]

Nest parasitism is a common phenomenon in many species of birds in which a female of one species lays her eggs in the nest of another species to be hatched and cared by the hosts. The nest parasitism evolved initially as a facultative strategy to use the nest of one species which has raised its brood or deserted nests and then further advanced into parasitism. The host species feed on a wide spectra of food resources, especially rich in protein and are insectivores, carnivores or omnivores in contrast to the very restrictive feeding habits of the parasite species. Parasitism cost for the host is often high which favour the evolution of host defence leading to a parallel evolution between adaptation and counter adaptation of host-parasite interaction. The understanding of breeding biology and ecology of nest parasitism provides important information for the population management of host and parasitic species to devise very specialized conservation strategies for the delicate interaction in the quickly evolving environmental scenario. [ABSTRACT FROM AUTHOR]

Kin discrimination, broadly defined as differential treatment of conspecifics according to their relatedness, could help biological systems direct cooperative behavior toward their relatives. Here we investigated the ability of the soil bacterium Bacillus subtilis to discriminate kin from nonkin in the context of swarming, a cooperative multicellular behavior. We tested a collection of sympatric conspecifics from soil in pairwise combinations and found that despite their history of coexistence, the vast majority formed distinct boundaries when the swarms met. Some swarms did merge, and most interestingly, this behavior was only seen in the most highly related strain pairs. Overall the swarm interaction phenotype strongly correlated with phylogenetic relatedness, indicative of kin discrimination. Using a subset of strains, we examined cocolonization patterns on plant roots. Pairs of kin strains were able to cocolonize roots and formed a mixed-strain biofilm. In contrast, inoculating roots with pairs of nonkin strains resulted in biofilms consisting primarily of one strain, suggestive of an antagonistic interaction among nonkin strains. This study firmly establishes kin discrimination in a bacterial multicellular setting and suggests its potential effect on ecological interactions. [ABSTRACT FROM AUTHOR]

Background. Exoenzyme-producing gut microbiota and their likely use as probionts have been widely investigated in major carps. However, reports on exoenzyme-producing capacity together with inhibition of fish pathogens are scarce. The presently reported study aimed at characterization of novel probionts from the gastro-intestinal (GI) tract of an Indian major carp--catla, Catla catla (Hamilton, 1822) depending upon extracellular enzyme-production, antagonism against Aeromonas spp., growth in fish mucus, bile tolerance, and bio-safety to the target fish. Materials and methods. GI tracts were divided into proximal and distal parts, homogenized, and plated onto selective media plates following enrichment culture technique. Exoenzyme-producing isolates were selected through qualitative and quantitative assay of 6 enzymes. Inhibition of Aeromonas spp. was tested through 'cross-streaking' and 'double-layer' method. Tolerance to GI condition was determined by growth in sterilized fish mucus and exposure to bile juice. Bio-safety evaluation was done by intra-peritoneal injection of live candidate probiotics and co-culture with autochthonous gut bacteria. Further, 16S rDNA fragments from the putative probiotics were sequenced, edited, analysed, identified, and deposited to the GenBank. Results. Seventeen potent isolates were primarily selected through the ability of producing extracellular enzymes, viz., amylase, protease, lipase, cellulase, phytase, and xylanase. Further study portraying antagonism against Aeromonas salmonicida, A. hydrophila, and A. veronii led to select the strains CCH1A and CCH1Ph as putative probiotics. Both the strains were competent to grow in intestinal mucus and could resist diluted bile juice (9% and 10.5%, respectively). The isolates did not produce any disease symptom or mortality in Catla catla fi ngerlings during the 21 day trial and were competent to grow with other autochthonous isolates. On the basis of phenotypic characteristics and 16S rDNA sequence analysis, the strains CCH1A and CCHIPh were identified as Bacillus aerius (KF623288) and Bacillus sonorensis (KF623289), respectively. Conclusion. Exoenzyme-producing gut bacteria may inhibit the growth of pathogenic Aeromonas spp. and tolerate gastrointestinal condition. Further research is inevitable to explore their potentialities in aquaculture. [ABSTRACT FROM AUTHOR]

The integration of physiological mechanisms into life-history theory is an emerging frontier in our understanding of the constraints and drivers of life-history evolution. Dynamic patterns of antagonism between developmental and immunological pathways in juvenile insects illustrate the importance of mechanisms for determining life-history strategy optima in the face of trade-offs. For example, developmental interference occurs when developmental processes transiently take priority over resources or pathway architecture, preventing allocation to immunity or other traits. We designed a within-host model of infected larval development to explore the impact of developmental dynamics on optimal resource mobilization and allocation strategies as well as on larval resistance and tolerance phenotypes. The model incorporates mechanism-inspired functional forms of developmental interference with immunity against parasites that attack specific larval stages. We find that developmental interference generally increases optimal investment in constitutive immunity and decreases optimal resource mobilization rates, but the results are sensitive to the developmental stage at first infection. Moreover, developmental interference reduces resistance but generally increases tolerance of infection. We demonstrate the potential impact of these dynamics on empirical estimates of host susceptibility and discuss the general implications of incorporating realistic physiological mechanisms and developmental dynamics for life-history theory in insects and other organisms. [ABSTRACT FROM AUTHOR]

A fundamental assumption of coexistence theory is that competition inevitably decreases species diversity. Consequently, in the quest to understand the ecological regulators of diversity, there has been a great deal of focus on processes with the potential to reduce competitive exclusion. However, the notion that competition must decrease diversity is largely based on the outcome of two-species interaction experiments and models, despite the fact that species rarely interact only in pairs in natural systems. In a field experiment, we found that competition among native perennial plants in multispecies assemblages was far weaker than competition between those same species in pairwise arrangements and that indirect interactions appeared to weaken direct competitive effects. These results suggest that community assembly theory based on pairwise approaches may overestimate the strength of competition and likelihood of competitive exclusion in species-rich communities. We also found that Centaurea stoebe, a North American invader, retained strong competitive effects when competing against North American natives in both pairwise and multi-species assemblages. Our experimental results support an emerging body of theory suggesting that complex networks of competing species may generate strong indirect interactions that can maintain diversity and that ecological differentiation may not be necessary to attenuate competition. [ABSTRACT FROM AUTHOR]

The transition from a planktonic larval stage to a benthic or demersal juvenile stage is a crucial event in the life history of coral reef fishes, and recruitment success has a strong influence on reef-fish population size. Post-settlement predation is thought to limit recruitment success. Most studies on post-settlement predation have focused on piscivorous reef fishes. However, recent studies in the tropical Pacific Ocean suggest that blood-feeding ectoparasites may also be an important source of predation. Here we provide further evidence that a gnathiid ectoparasite is capable of such "micropredation" on settlement-stage fish in the eastern Caribbean Sea. On 12 occasions in May–August, 2014 and 2015, during plankton light-trap recovery, we observed postsettlement fishes from the families Apogonidae, Bothidae, Gobiidae, Labrisomidae, and Tripterygiidae with attached ectoparasitic juvenile gnathiid isopods. In one laboratory experiment in which 10 settlement-stage French grunt, Haemulon flavolineatum (Desmarest, 1823), were fed upon by an average of one gnathiid per fish, all fish died compared to none in the control group. In a subsequent experiment in which individual settlement-stage French grunt were exposed to 0–3 gnathiids each, all 50 fish that were fed upon by at least one gnathiid died, compared with only one of 78 that were not fed on by any gnathiids. Combined with observations on damselfishes from the Pacific Ocean, these findings suggest that gnathiids are capable of micropredation on larval fish at time of reef settlement and that micropredation should be further evaluated as a factor affecting success of settlement and thus recruitment success of coral reef fishes. [ABSTRACT FROM AUTHOR]

Social parasitism is occasionally found in some Polistes and Vespa species, such as Vespa dybowskii. We report a discovey of interspecific facultative social parasitism by Polistes sp. (possibly P. mandarinus) on Polistes djakonovi Kostylev in two rural areas of South Korea. P. djakonovi is very similar to Polistes sp. in its body color patterns except that the mark on the clypeus is different. In nest 1 (65 cells), we found 5 females of P. djakonovi and 4 females of Polistes sp. on 30 July 2014, whereas nest 2 (102 cells) contained 12 females and 16 males of P. djakonovi, and 3 females of Polistes sp. on 28 August 2013. Although we found the two nests in July and August, P. djakonovi seems to have been exploited by Polistes sp. at the end of the preemergence period (early to mid-June). The two nests found in this study had mainly white cocoon caps of P. djakonovi with several yellow ones of Polistes sp. In most cases of social parasitism, intruders have a larger size of the body or some body parts than the host in order to usurp the host; in contrast, this study showed that the hosts had lager bodies than the intruders. [ABSTRACT FROM AUTHOR]

Both estrogenic and anti-estrogenic activity has been observed in water samples. Some studies have suggested that dissolved organic carbon (DOC), which can be co-extracted during sample enrichment, contributes to the apparent antagonistic effect. DOC has a high sorption capacity for the estrogen receptor (ER) agonist 17β-estradiol, which may reduce the available 17β-estradiol concentration in the antagonist testing mode and potentially lead to apparent antagonism. The aim of the study was to determine the influence of DOC when assessing antagonism in an ER reporter gene assay. The presence of DOC shifted the 17β-estradiol concentration-effect curve to higher concentrations, increasing the nominal EC 50 value by up to 0.3 log units. However, this shift was within the usual variability associated with repeated measurements of concentration-effect curves. This shift was not due to DOC being an antagonist itself or interfering with fluorescence measurements, but was due to DOC reducing the bioavailability of 17β-estradiol. This was demonstrated by modelling the DOC sorption corrected 17β-estradiol concentration using experimental DOC-water partition coefficients ( K DOC ). While the shift in the 17β-estradiol concentration-effect curve was minor, sorption of 17β-estradiol to DOC can have an impact when assessing antagonism. At the EC 50 agonist concentration, both modelled and experimental results showed that DOC at concentrations similar to that co-extracted in water samples caused suppression of the agonist at levels that would be classified as antagonism. The suppression was less pronounced at the EC 80 agonist concentration, hence this is recommended when assessing antagonism of DOC rich samples, such as surface water and wastewater. [ABSTRACT FROM AUTHOR]

There is increasing recognition of the importance of assessing both agonism and antagonism in parallel for environmental samples. Cell-based in vitro assays have the advantage over receptor binding assays as they are able to differentiate between agonist and antagonist activity, but at present there is no standardized approach to assess antagonism in vitro , and in particular the competing agonist concentration can vary in the literature anywhere from half maximal to maximal effect concentrations. In this study, we investigated the influence of changing agonist concentrations in the estrogen receptor alpha (ERα), progesterone receptor (PR) and glucocorticoid receptor (GR) assays run in antagonist mode. The antagonistic effect varied by over two orders of magnitude when using the range of agonist concentrations applied in the literature, clearly indicating the need for standardization. By comparing antagonist EC 50 values with different background agonist concentrations, an EC 80 background agonist concentration is recommended when assessing antagonism in vitro to optimise both assay sensitivity and reproducibility. [ABSTRACT FROM AUTHOR]

Green peach aphid (Myzus persicae Sulzer) (Hemiptera: Aphididae) is a serious greenhouse pest with a short generation time, parthenogenetic reproduction and a broad host range. Banker plant systems are becoming a more common form of biological control for this pest. This system consists of grain "banker plants" infested with R. padi, an alternative hosts for the parasitoid Aphidius colemani. Thus A. colemani can reproduce on the banker plant when M. persicae populations are low. This system can increase pest suppression; however, like other biological control tools, efficacy is inconsistent. One reason is because several different grain species have been used. Our studies determined if there were benefits to planting interspecific mixture banker plants, similar to when open agricultural systems use mixed cropping. Our study found that although banker plants grow larger when planted as mixtures this added plant growth does not increase in the number of aphids, or mummies an individual banker plant can sustain. Rye banker plants grew larger, and sustained more mummies than the other species we tested, but barley banker plants resulted in a similar number of aphids in a more condensed area. Ultimately, we did not see any differences in pest suppression between monoculture banker plants, mixture banker plants, or our augmentative release treatment. However, using banker plants resulted in more female parasitoids than the augmentative release, a benefit to using banker plant systems. [ABSTRACT FROM AUTHOR]

We documented natural behaviour and staged intersexual interactions of Habronattus americanus jumping spiders in the wild in order to clarify three aspects of their mating strategies: (1) Do males invest more than females in locomotory mate search? (2) Do females exert strong mate choice? (3) Do direct contests occur among males? Males apparently invested heavily in mate search, travelling more than females yet eating nothing. Conversely, females frequently hunted and spent 10% of their time feeding. Females encountered one male per hour, likely affording them a high degree of choice among prospective mates. Accordingly, they promoted the termination of each interaction and ultimately rejected nearly all courting males. Male-male interactions were brief and did not feature direct antagonism. Our findings suggest that mate competition in H. americanus is characterized by male scramble competition for dispersed females, and that female mate choice may exert strong selection on male sexual display traits. [ABSTRACT FROM AUTHOR]

In order for endophytic fungi to grow asymptomatically in their plant hosts, a balance of antagonisms is presumed to exist between host defence and fungal virulence. However, in planta, endophytic fungi must deal with multiple organismal interactions, primarily with bacteria and other fungi. We hypothesize that the plethora of antibacterial and antifungal metabolites that endophytic fungi produce has the function of maintaining balances of antagonisms with microbial competitors, resulting in a compatible multipartite symbiosis. Results obtained from co-cultures of endophytic and rhizospheric fungi with Pseudomonas aeruginosa and of endophytic fungi with Hymenoscyphus fraxineus, pathogen of the European ash, corroborate this hypothesis. [ABSTRACT FROM AUTHOR]

Symbionts can have mutualistic effects that increase their host’s fitness and/or parasitic effects that reduce it. Which of these strategies evolves depends in part on the balance of their costs and benefits to the symbiont. We have examined these questions in Wolbachia, a vertically transmitted endosymbiont of insects that can provide protection against viral infection and/or parasitically manipulate its hosts’ reproduction. Across multiple symbiont strains we find that the parasitic phenotype of cytoplasmic incompatibility and antiviral protection are uncorrelated. Strong antiviral protection is associated with substantial reductions in other fitness-related traits, whereas no such trade-off was detected for cytoplasmic incompatibility. The reason for this difference is likely that antiviral protection requires high symbiont densities but cytoplasmic incompatibility does not. These results are important for the use of Wolbachia to block dengue virus transmission by mosquitoes, as natural selection to reduce these costs may lead to reduced symbiont density and the loss of antiviral protection. [ABSTRACT FROM AUTHOR]

One of the most important orange fruit diseases is blue mold which cause by Penicillium italicum that is responsible for important economic losses. This study investigated biochemical changes in exo-mesocarp layers of orange fruits related to hostpathogen- yeast interactions. Initial result showed that among eight strains isolated, the most effective antagonist were belonged to two species of Pichia kluyveri (M45) and Rhodotorula mucilaginosa (M61). These isolates were selected for biochemical evaluation. In order to assessment of biochemical changes, the orange fruits were inoculated with 40 μl of yeast cell suspension and after 24 h, the wounds were inoculated with 20 μl of conidial suspension of P. italicum. The analysis of variance showed that all of the measured biochemical characterises were significant in both layers by treatments (yeast isolates; pathogen; yeast isolates + pathogen and control) (P ≥ 0.01), including POD, CAT and β-1, 3-glucanase activities and total phenolic compounds. Also result showed that when the yeast isolates (M45 or M54) were inoculated into wounds with the pathogen, it stimulated the orange to increase produce of total phenol and enzymes activity (POD, CAT and β-1, 3-glucanase) and these changes were related to incubation time. The result showed that understanding biochemical mechanism derived from plant-pathogen-antagonist interactions is essential for investigating the dynamics of infectious processes. [ABSTRACT FROM AUTHOR]

Sexual conflicts and their evolutionary outcomes may be influenced by population- specific features such as mating system and ecological context; however, very few studies have investigated the link between sexual conflict and mating system. The self-compatible, mixed-mating hermaphrodite Collinsia heterophylla (Plantaginaceae) is thought to exhibit a sexual conflict over timing of stigma receptivity. This conflict involves (i) delayed stigma receptivity, which intensifies pollen competition, and (ii) early fertilization forced by pollen, which reduces seed set. We investigated the potential for the conflict to occur under field conditions and performed glasshouse crosses within eight populations to assess its consistency across populations. Flowers were visited, and produced seeds after pollination, at all developmental stages, suggesting that the conflict can be of significance under natural conditions. In the glasshouse, early pollination imposed costs in all populations. Overall, the timing of first seed set was most strongly affected by the maternal parent, denoting stronger female than male ability to influence the onset of stigma receptivity. Crosses also revealed a negative relationship between donor- and recipient-related onset of receptivity within individuals, a novel result hinting at trade-offs in sex allocation or a history of antagonistic selection. Neither timing of stigma receptivity, timing of first seed set, nor pollen competitive ability covaried with population outcrossing rate. In conclusion, these results indicate that sexually antagonistic selection may be present in varying degrees in different populations of C. heterophylla, but this variation does not appear to be directly related to mating system variation. [ABSTRACT FROM AUTHOR]

Interactions between flowers and their visitors span the spectrum from mutualism to antagonism. The literature is rich in studies focusing on mutualism, but nectar robbery has mostly been investigated using phytocentric approaches focused on only a few plant species. To fill this gap, we studied the interactions between a nectar-robbing hermit hummingbird, Phaethornis ruber, and the array of flowers it visits. First, based on a literature review of the interactions involving P. ruber, we characterized the association of floral larceny to floral phenotype. We then experimentally examined the effects of nectar robbing on nectar standing crop and number of visits of the pollinators to the flowers of Canna paniculata. Finally, we asked whether the incorporation of illegitimate interactions into the analysis affects plant-hummingbird network structure. We identified 97 plant species visited by P. ruber and found that P. ruber engaged in floral larceny in almost 30 % of these species. Nectar robbery was especially common in flowers with longer corolla. In terms of the effect on C. paniculata, the depletion of nectar due to robbery by P. ruber was associated with decreased visitation rates of legitimate pollinators. At the community level, the inclusion of the illegitimate visits of P. ruber resulted in modifications of how modules within the network were organized, notably giving rise to a new module consisting of P. ruber and mostly robbed flowers. However, although illegitimate visits constituted approximately 9 % of all interactions in the network, changes in nestedness, modularity, and network-level specialization were minor. Our results indicate that although a flower robber may have a strong effect on the pollination of a particular plant species, the inclusion of its illegitimate interactions has limited capacity to change overall network structure. [ABSTRACT FROM AUTHOR]

Obstructive sleep apnoea (OSA) is highly prevalent in hypertensive patients, particularly those with drug resistance. Evidence from animal experiments, epidemiologic studies and clinical trials strongly suggest a causal link. Mechanistic studies argue for increased sympathetic neural activity and endothelial dysfunction. However, disturbances in fluid volume regulation and distribution may also be involved in the pathogenesis of these two conditions. Several studies have shown a high prevalence of OSA in fluid-retaining states including hypertension, a direct relationship between the severity of OSA and the volume of fluid displaced from the legs to the neck during sleep, and a decrease in upper airway cross-sectional area in response to graded lower body positive pressure. Treatments targeting fluid retention and redistribution, including diuretics, mineralocorticoid antagonists, exercise, and possibly renal denervation lower blood pressure and reduce the apnoea-hypopnoea index, a measure of OSA severity. From these observations, it has been postulated that during the daytime, excess fluid collects in the lower extremities due to gravity, and on lying down overnight is redistributed rostrally to the neck, where it may narrow the upper airway and increase its collapsibility, predisposing to OSA when pharyngeal dilator muscle activity decreases during sleep. This article discusses the associations between OSA and hypertension and reviews the evidence for fluid accumulation and its nocturnal rostral redistribution in the pathogenesis of OSA in hypertensive patients. [ABSTRACT FROM AUTHOR]

Conspicuousness, or having high contrast relative to the surrounding background, is a common feature of unpalatable species. Several hypotheses have been proposed to explain the occurrence of conspicuousness, and while most involve the role of conspicuousness as a direct signal of unpalatability to potential predators, one hypothesis suggests that exaggerated conspicuousness may evolve in unpalatable species to reduce predator confusion with palatable species (potential Batesian mimics). This hypothesis of antagonistic coevolution between palatable and unpalatable species hinges on the 'cost of conspicuousness', in which conspicuousness increases the likelihood of predation more in palatable species than in unpalatable species. Under this mimicry scenario, four patterns are expected: (i) mimics will more closely resemble local models than models from other localities, (ii) there will be a positive relationship between mimic and model conspicuousness, (iii) models will be more conspicuous in the presence of mimics, and (iv) when models and mimics differ in conspicuousness, mimics will be less conspicuous than models. We tested these predictions in the salamander mimicry system involving Notophthalmus viridescens (model) and one colour morph of Plethodon cinereus (mimic). All predictions were supported, indicating that selection for Batesian mimicry not only influences the evolution of mimics, but also the evolution of the models they resemble. These findings indicate that mimicry plays a large role in the evolution of model warning signals, particularly influencing the evolution of conspicuousness. [ABSTRACT FROM AUTHOR]

Parasitism is expected to impact host morbidity or mortality, although the fitness costs of parasitism have rarely been quantified for wildlife hosts. Tapeworms in the genus Taenia exploit a variety of vertebrates, including livestock, humans, and geladas ( Theropithecus gelada), monkeys endemic to the alpine grasslands of Ethiopia. Despite Taenia's adverse societal and economic impacts, we know little about the prevalence of disease associated with Taenia infection in wildlife or the impacts of this disease on host health, mortality and reproduction. We monitored geladas at Guassa, Ethiopia over a continuous 6½ year period for external evidence (cysts or coenuri) of Taenia-associated disease (coenurosis) and evaluated the impact of coenurosis on host survival and reproduction. We also identified (through genetic and histological analyses) the tapeworms causing coenurosis in wild geladas at Guassa as Taenia serialis. Nearly 1/3 of adult geladas at Guassa possessed ≥1 coenurus at some point in the study. Coenurosis adversely impacted gelada survival and reproduction at Guassa and this impact spanned two generations: adults with coenuri suffered higher mortality than members of their sex without coenuri and offspring of females with coenuri also suffered higher mortality. Coenurosis also negatively affected adult reproduction, lengthening interbirth intervals and reducing the likelihood that males successfully assumed reproductive control over units of females. Our study provides the first empirical evidence that coenurosis increases mortality and reduces fertility in wild nonhuman primate hosts. Our research highlights the value of longitudinal monitoring of individually recognized animals in natural populations for advancing knowledge of parasite-host evolutionary dynamics and offering clues to the etiology and control of infectious disease. Am. J. Primatol. 77:579-594, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Splanchnic angiogenesis in liver cirrhosis often leads to complications as gastroesophageal variceal hemorrhage and the treatment efficacy is adversely affected by poor portal-systemic collateral vasoresponsiveness related to nitric oxide (NO). Purinergic receptor subtype P2X7 participates in the modulation of inflammation, angiogenesis, fibrogenesis and vasoresponsiveness, but the relevant influence in cirrhosis is unknown. Common bile duct-ligated (CBDL) or sham-operated Spraque-Dawley rats received brilliant blue G (BBG, a P2X7 antagonist and food additive) or vehicle from the 15th to 28th day after operations, then hemodynamics, mesenteric angiogenesis, portal-systemic shunting, liver fibrosis, and protein expressions of angiogenic and fibrogenic factors were evaluated. The influence of oxidized ATP (oATP, another P2X7 receptor antagonist) on the collateral vasoresponsiveness to arginine vasopressin (AVP) was also surveyed. BBG decreased superior mesenteric artery (SMA) flow, portal-systemic shunting, mesenteric vascular density, and mesenteric protein expressions of vascular endothelial growth factor (VEGF), VEGF receptor 2 (VEGFR2), phospho (p)-VEGFR2, platelet-derived growth factor (PDGF), PDGF receptor beta (PDGFRβ), cyclooxygenase (COX)-1, COX-2, and endothelial NO synthase (eNOS) in CBDL rats. BBG also ameliorated liver fibrosis and down-regulated hepatic interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), PDGF, IL-1β, transforming growth factor-beta (TGF-β), p-extracellular-signal-regulated kinases (ERK), and alpha-smooth muscle actin (α-SMA) expressions in CBDL rats. The collateral vasocontractility to AVP was enhanced by oATP. oATP down-regulated eNOS, inducible NOS (iNOS), VEGF, Akt, p-Akt, and nuclear factor-kappa B (NF-κB) expressions in splenorenal shunt, the most prominent intra-abdominal collateral vessel in rodents. P2X7 antagonism alleviates splanchnic hyperemia, severity of portal-systemic shunting, mesenteric angiogenesis, liver fibrosis, and enhances portal-systemic collateral vasoresponsiveness in cirrhotic rats. P2X7 blockade may be a feasible strategy to control cirrhosis and complications. [ABSTRACT FROM AUTHOR]

Allorecognition, the ability to distinguish 'self' from 'nonself' based on allelic differences at allorecognition loci, is common in all domains of life. Allorecognition restricts the opportunities for social parasitism, and is therefore crucial for the evolution of cooperation. However, the maintenance of allorecognition diversity provides a paradox. If allorecognition is costly relative to cooperation, common alleles will be favored. Thus, the cost of allorecognition may reduce the genetic variation upon which allorecognition crucially relies, a prediction now known as 'Crozier's paradox.' We establish the relative costs of allorecognition, and their consequences for the short-term evolution of recognition labels theoretically predicted by Crozier. We use fusion among colonies of the fungus Neurospora crassa, regulated by highly variable allorecognition genes, as an experimental model system. We demonstrate that fusion among colonies is mutually beneficial, relative to absence of fusion upon allorecognition. This benefit is due not only to absence of mutual antagonism, which occurs upon allorecognition, but also to an increase in colony size per se. We then experimentally demonstrate that the benefit of fusion selects against allorecognition diversity, as predicted by Crozier. We discuss what maintains allorecognition diversity. [ABSTRACT FROM AUTHOR]

The potential for complex synergistic or antagonistic interactions between multiple stressors presents one of the largest uncertainties when predicting ecological change but, despite common use of the terms in the scientific literature, a consensus on their operational definition is still lacking. The identification of synergism or antagonism is generally straightforward when stressors operate in the same direction, but if individual stressor effects oppose each other, the definition of synergism is paradoxical because what is synergistic to one stressor's effect direction is antagonistic to the others. In their highly cited meta-analysis, Crain et al. ( Ecology Letters, 11, 2008: 1304) assumed in situations with opposing individual effects that synergy only occurs when the cumulative effect is more negative than the additive sum of the opposing individual effects. We argue against this and propose a new systematic classification based on an additive effects model that combines the magnitude and response direction of the cumulative effect and the interaction effect. A new class of 'mitigating synergism' is identified, where cumulative effects are reversed and enhanced. We applied our directional classification to the dataset compiled by Crain et al. ( Ecology Letters, 11, 2008: 1304) to determine the prevalence of synergistic, antagonistic, and additive interactions. Compared to their original analysis, we report differences in the representation of interaction classes by interaction type and we document examples of mitigating synergism, highlighting the importance of incorporating individual stressor effect directions in the determination of synergisms and antagonisms. This is particularly pertinent given a general bias in ecology toward investigating and reporting adverse multiple stressor effects (double negative). We emphasize the need for reconsideration by the ecological community of the interpretation of synergism and antagonism in situations where individual stressor effects oppose each other or where cumulative effects are reversed and enhanced. [ABSTRACT FROM AUTHOR]

S. marcescens FS14 was isolated from an Atractylodes macrocephala Koidz plant that was infected by Fusarium oxysporum and showed symptoms of root rot. With the completion of the genome sequence of FS14, the first comprehensive comparative-genomic analysis of the Serratia genus was performed. Pan-genome and COG analyses showed that the majority of the conserved core genes are involved in basic cellular functions, while genomic factors such as prophages contribute considerably to genome diversity. Additionally, a Type I restriction-modification system, a Type III secretion system and tellurium resistance genes are found in only some Serratia species. Comparative analysis further identified that S. marcescens FS14 possesses multiple mechanisms for antagonism against other microorganisms, including the production of prodigiosin, bacteriocins, and multi-antibiotic resistant determinants as well as chitinases. The presence of two evolutionarily distinct Type VI secretion systems (T6SSs) in FS14 may provide further competitive advantages for FS14 against other microbes. To our knowledge, this is the first report of comparative analysis on T6SSs in the genus, which identifies four types of T6SSs in Serratia spp.. Competition bioassays of FS14 against the vital plant pathogenic bacterium Ralstonia solanacearum and fungi Fusarium oxysporum and Sclerotinia sclerotiorum were performed to support our genomic analyses, in which FS14 demonstrated high antagonistic activities against both bacterial and fungal phytopathogens. [ABSTRACT FROM AUTHOR]

A total of 53 Wickerhamomyces anomalus strains were examined for antagonistic activity, including the nomenclature types of the species with the names presently considered synonymous. Over 70% of the strains exhibited antibiotic activity. According to the action spectra of intraspecific activity, the strains fell into three groups, while according to their activity against other Wickerhamomyces species and phylogenetically related Candida species they formed five subgroups. Antibiotic agents (mostly mycocins) varied in their physicochemical properties [ABSTRACT FROM AUTHOR]

Sexual antagonism occurs when there is a positive intersexual genetic correlation in trait expression but opposite fitness effects of the trait(s) in males and females. As such, it constrains the evolution of sexual dimorphism and may therefore have implications for adaptive evolution. There is currently considerable evidence for the existence of sexually antagonistic genetic variation in laboratory and natural populations, but how sexual antagonism interacts with other evolutionary phenomena is still poorly understood in many cases. Here, we explore how self-fertilization and inbreeding affect the maintenance of polymorphism for sexually antagonistic loci. We expected a priori that selfing should reduce the region of polymorphism, as inbreeding reduces the frequency of heterozygotes and speeds fixation. This expectation was supported, but although previous results suggest that the more an allele that is deleterious to one sex is dominant in that sex, the smaller the region of parameter space that will admit polymorphism, we found that this effect is weakened by self-fertilization. However, the effect of inbreeding is not strong enough to completely cancel out the effect of dominance: For a given frequency of inbreeding, it will still be the case that the more dominant the alleles are in their deleterious context, the smaller the region of parameter space in which they can exist at polymorphism. [ABSTRACT FROM AUTHOR]

Ant foraging on foliage can substantially affect how phytophagous insects use host plants and represents a high predation risk for caterpillars, which are important folivores. Ant-plant-herbivore interactions are especially pervasive in cerrado savanna due to continuous ant visitation to liquid food sources on foliage (extrafloral nectaries, insect honeydew). While searching for liquid rewards on plants, aggressive ants frequently attack or kill insect herbivores, decreasing their numbers., Because ants vary in diet and aggressiveness, their effect on herbivores also varies. Additionally, the differential occurrence of ant attractants (plant and insect exudates) on foliage produces variable levels of ant foraging within local floras and among localities. Here, we investigate how variation of ant communities and of traits among host plant species (presence or absence of ant attractants) can change the effect of carnivores (predatory ants) on herbivore communities (caterpillars) in a cerrado savanna landscape., We sampled caterpillars and foliage-foraging ants in four cerrado localities (70-460 km apart). We found that: (i) caterpillar infestation was negatively related with ant visitation to plants; (ii) this relationship depended on local ant abundance and species composition, and on local preference by ants for plants with liquid attractants; (iii) this was not related to local plant richness or plant size; (iv) the relationship between the presence of ant attractants and caterpillar abundance varied among sites from negative to neutral; and (v) caterpillars feeding on plants with ant attractants are more resistant to ant predation than those feeding on plants lacking attractants., Liquid food on foliage mediates host plant quality for lepidopterans by promoting generalized ant-caterpillar antagonism. Our study in cerrado shows that the negative effects of generalist predatory ants on herbivores are detectable at a community level, affecting patterns of abundance and host plant use by lepidopterans., The magnitude of ant-induced effects on caterpillar occurrence across the cerrado landscape may depend on how ants use plants locally and how they respond to liquid food on plants at different habitats. This study enhances the relevance of plant-ant and ant-herbivore interactions in cerrado and highlights the importance of a tritrophic perspective in this ant-rich environment. [ABSTRACT FROM AUTHOR]

Odor activity value (OAV) has been widely used for the assessment of odor pollution from various sources. However, little attention has been paid to the extreme OAV variation and potential inaccuracies of odor contribution assessment caused by odor interaction effects. The objective of this study is to assess the odor interaction effect for precise assessment of odor contribution. In this paper, samples were collected from a food waste disposal plant, and analyzed by instrumental and olfactory method to conclude odorants' occurrence and OAV. Then odor activity value coefficient (γ) was first proposed to evaluate the type and the level of binary interaction effects based on determination of OAV variation. By multiplying OAV and γ, odor activity factor (OAF) was used to reflect the real OAV. Correlation between the sum of OAF and odor concentration reached 80.0 ± 5.7%, which was 10 times higher than the sum of OAV used before. Results showed that hydrogen sulfide contributed most (annual average 66.4 ± 15.8%) to odor pollution in the waste disposal plant. However, as odor intensity of samples in summer rising, odor contribution of trimethylamine increased to 48.3 ± 3.7% by the strong synergistic interaction effect, while odor contribution of phenol decreased to 0.1 ± 0.02% for the increasing antagonistic interaction effect. [ABSTRACT FROM AUTHOR]

Although a negative covariance between parasite load and sexually selected trait expression is a requirement of few sexual selection models, such a covariance may be a general result of life-history allocation trade-offs. If both allocation to sexually selected traits and to somatic maintenance (immunocompetence) are condition dependent, then in populations where individuals vary in condition, a positive covariance between trait expression and immunocompetence, and thus a negative covariance between trait and parasite load, is expected. We test the prediction that parasite load is generally related to the expression of sexual dimorphism across two breeding seasons in a wild salamander population and show that males have higher trematode parasite loads for their body size than females and that a key sexually selected trait covaries negatively with parasite load in males. We found evidence of a weaker negative relationship between the analogous female trait and parasite infection. These results underscore that parasite infection may covary with expression of sexually selected traits, both within and among species, regardless of the model of sexual selection, and also suggest that the evolution of condition dependence in males may affect the evolution of female trait expression. [ABSTRACT FROM AUTHOR]

The article discusses how predators can impact primary producers through cascade effects in ecological webs and how plants can benefit from antagonistic and mutualistic interactions with bears. Topics include how the consumption of ants by black bears can impact plants due to weakened protection of herbivores by depleted ant populations, the relationship between mutualisms and trophic cascade theory, and how this impacts predator management.

Transgenic crop pyramids producing two or more Bacillus thuringiensis (Bt) toxins that kill the same insect pest have been widely used to delay evolution of pest resistance. To assess the potential of pyramids to achieve this goal, we analyze data from 38 studies that report effects of ten Bt toxins used in transgenic crops against 15 insect pests. We find that compared with optimal low levels of insect survival, survival on currently used pyramids is often higher for both susceptible insects and insects resistant to one of the toxins in the pyramid. Furthermore, we find that cross-resistance and antagonism between toxins used in pyramids are common, and that these problems are associated with the similarity of the amino acid sequences of domains II and III of the toxins, respectively. This analysis should assist in future pyramid design and the development of sustainable resistance management strategies. [ABSTRACT FROM AUTHOR]

Controlling toxigenic Fusarium graminearum (FG) is challenging. A bacterial strain (S76-3, identified as Bacillus amyloliquefaciens) that was isolated from diseased wheat spikes in the field displayed strong antifungal activity against FG. Reverse-phase high performance liquid chromatography and electrospray ionization mass spectrometry analyses revealed that S76-3 produced three classes of cyclic lipopeptides including iturin, plipastatin and surfactin. Each class consisted of several different molecules. The iturin and plipastatin fractions strongly inhibited FG; the surfactin fractions did not. The most abundant compound that had antagonistic activity from the iturin fraction was iturin A (m/z 1043.35); the most abundant active compound from the plipastatin fraction was plipastatin A (m/z 1463.90). These compounds were analyzed with collision-induced dissociation mass spectrometry. The two purified compounds displayed strong fungicidal activity, completely killing conidial spores at the minimal inhibitory concentration range of 50 µg/ml (iturin A) and 100 µg/ml (plipastatin A). Optical and fluorescence microscopy analyses revealed severe morphological changes in conidia and substantial distortions in FG hyphae treated with iturin A or plipastatin A. Iturin A caused leakage and/or inactivation of FG cellular contents and plipastatin A caused vacuolation. Time-lapse imaging of dynamic antagonistic processes illustrated that iturin A caused distortion and conglobation along hyphae and inhibited branch formation and growth, while plipastatin A caused conglobation in young hyphae and branch tips. Transmission electron microscopy analyses demonstrated that the cell walls of conidia and hyphae of iturin A and plipastatin A treated FG had large gaps and that their plasma membranes were severely damaged and separated from cell walls. [ABSTRACT FROM AUTHOR]

Plant-pollinator associations are often seen as purely mutualistic, while in reality they can be more complex. Indeed they may also display a diverse array of antagonistic interactions, such as competition and victim–exploiter interactions. In some cases mutualistic and antagonistic interactions are carried-out by the same species but at different life-stages. As a consequence, population structure affects the balance of inter-specific associations, a topic that is receiving increased attention. In this paper, we developed a model that captures the basic features of the interaction between a flowering plant and an insect with a larval stage that feeds on the plant’s vegetative tissues (e.g. leaves) and an adult pollinator stage. Our model is able to display a rich set of dynamics, the most remarkable of which involves victim–exploiter oscillations that allow plants to attain abundances above their carrying capacities and the periodic alternation between states dominated by mutualism or antagonism. Our study indicates that changes in the insect’s life cycle can modify the balance between mutualism and antagonism, causing important qualitative changes in the interaction dynamics. These changes in the life cycle could be caused by a variety of external drivers, such as temperature, plant nutrients, pesticides and changes in the diet of adult pollinators. [ABSTRACT FROM AUTHOR]

In two experiments, using a modified task-cueing paradigm, participants switched among a set of four tasks that was on some trials reduced to two by a pre-cue preceding the task cue. A pre-cue temporarily restricting the options to two candidate tasks facilitated performance on switch trials to a much larger extent than on repeat trials. This observation is interpreted as an indication of a short-term restructuring of a global task representation by implementing antagonistic constraints among the representations of the two remaining candidate tasks. [ABSTRACT FROM AUTHOR]

Studies of when youth classify academic achievement in racial terms have focused on the racial classification of behaviors and individuals. However, institutions—including schools—may also be racially classified. Drawing on a comparative interview study, we examine the school contexts that prompt urban black students to classify schools in racial terms. Through Diversify, a busing program, one group of black students attended affluent suburban schools with white-dominated achievement hierarchies (n = 38). Diversify students assigned schools to categories of whiteness or blackness that equated whiteness with achievement and blackness with academic deficiency. Students waitlisted for Diversify (n = 16) attended urban schools without white-dominated achievement hierarchies. These students did not classify schools as white or black, based on academic quality. We assert that scholars may productively conceive of schools, not just individual students, as sites of potential racial classification. Furthermore, the racial classification of schools reinforces antagonism between black students attending ‘‘white’’ and ‘‘black’’ schools and perpetuates harmful racial stereotypes. [ABSTRACT FROM PUBLISHER]

Conservatism in species interaction, meaning that related species tend to interact with similar partners, is an important feature of ecological interactions. Studies at community scale highlight variations in conservatism strength depending on the characteristics of the ecological interaction studied. However, the heterogeneity of datasets and methods used prevent to compare results between mutualistic and antagonistic networks. Here we perform such a comparison by taking plant-insect communities as a study case, with data on plant-herbivore and plant-pollinator networks. Our analysis reveals that plants acting as resources for herbivores exhibit the strongest conservatism in species interaction among the four interacting groups. Conservatism levels are similar for insect pollinators, insect herbivores and plants as interacting partners of pollinators, although insect pollinators tend to have a slightly higher conservatism than the two others. Our results thus clearly support the current view that within antagonistic networks, conservatism is stronger for species as resources than for species as consumer. Although the pattern tends to be opposite for plant-pollinator networks, our results suggest that asymmetry in conservatism is much less pronounced between the pollinators and the plant they interact with. We discuss these differences in conservatism strength in relation with the processes structuring plant-insect communities. [ABSTRACT FROM AUTHOR]

Recently, a theoretical hypothesis was proposed that the coexistence of antagonism and mutualism may stabilize ecological community and even give rise to a positive complexity-stability relationship (interaction-type diversity hypothesis). This hypothesis was derived from an analysis of community model, which was developed based on two specific assumptions about the interaction strengths: those are, (i) different interaction types, antagonism and mutualism, have quantitatively comparable magnitude of effects to population growth; and (ii) interaction strength decreases with increasing interaction links of the same interaction type. However, those assumptions do not necessarily hold in real ecosystems, leaving unclear how robust this hypothesis is. Here, using a model with those two assumptions relaxed, we show (i) that the balance of interaction strength is necessary for the positive complexity effect to arise and (ii) that interaction-type diversity hypothesis may still hold when interaction strength decreases with increasing links of all interaction type for some species. [ABSTRACT FROM AUTHOR]

Increasing global temperature and sea-level rise have led to concern about expansions in the distribution and prevalence of complex-lifecycle parasites (CLPs). Indeed, numerous environmental variables can influence the infectivity and reproductive output of many pathogens. Digenean trematodes are CLPs with intermediate invertebrate and definitive vertebrate hosts. Global warming and sea level rise may affect these hosts to varying degrees, and the effect of increasing temperature on parasite prevalence has proven to be nonlinear and difficult to predict. Projecting the response of parasites to anthropogenic climate change is vital for human health, and a longer term perspective (104 y) offered by the subfossil record is necessary to complement the experimental and historical approaches of shorter temporal duration (10-1 to 103 y). We demonstrate, using a high-resolution 9,600-y record of trematode parasite traces in bivalve hosts from the Holocene Pearl River Delta, that prevalence was significantly higher during the earliest stages of sea level rise, significantly lower during the maximum transgression, and statistically indistinguishable in the other stages of sea-level rise and delta progradation. This stratigraphic paleobiological pattern represents the only long-term high-resolution record of pathogen response to global change, is consistent with fossil and recent data from other marine basins, and is instructive regarding the future of disease. We predict an increase in trematode prevalence concurrent with anthropogenic warming and marine transgression, with negative implications for estuarine macrobenthos, marine fisheries, and human health. [ABSTRACT FROM AUTHOR]